I can never GET my printer to work. I thought I fixed the problem last week by doing the shut down 'print spooler' service and then restarting it in 'services'. It successfully printed several documents after that. But I just went to print something right now and it didn't work.

OS: Windows 10
Printer: HP LaserJet 1200 Series

Here's what I've tried so far:

https://thetechhacker.com/2017/10/17/fix-printer-offline-problem-windows-10/

At that site, in Method 1, my printer does not show up in the LIST of printers. In Method 2, stopping and restarting the print spooler service does not fix anything this week.

Rebooting the computer does not help.

Plugging the printer into different USB ports doesn't fix anything.

https://support.hp.com/in-en/topic/printscandoctor-printing-problems#fixPrintingContainer2

Installing HP Print and Scan Doctor doesn't fix the problem. The app actually sees the printer, which is good, but it doesn't fix the problem. It says there are 3 HP LaserJet 1200s installed. The actual HP LaserJet 1200, HP LaserJet 1200 Copy 1 and HP LaserJet 1200 Copy 2. I clicked on all of them and pressed 'Retry' and 'Connect' but it doesn't connect any of them.

https://www.lifewire.com/fix-usb-ports-4151908

01: Restart the computer. Doesn't fix the problem.

02: Physically inspect the USB ports. I am not going to know if there's anything wrong by taking the computer apart and visually inspecting them. The ports work when I plug anything else into them, so I assume the USB ports are fine. The problem is, the computer does not see the printer.

03: Plug the device into another USB port. I have tried every USB port and it makes no difference.

04: Swap to a different USB cable. I can't because the USB cable for the printer is hardwired.

05: Plug printer into different computer. Haven't tried that.

06: Try plugging in a different USB device. Tried, they all work.

07: Check device manager and disable the USB controllers, then restart computer. Did that, doesn't fix the problem.
Scan for hardware changes: did that, doesn't fix the problem.Most likely the printer  itself is bad.
HP LaserJet 1200 Series is a pricey printer.
 Over $300  For that price the dealer ought to replace it.
Did it have a warranty?

I have successfully used the printer before, on this computer, as I said. The last time was about 2 weeks ago. But for some reason, every time I get it to work, it only works for that day, then Windows does something that causes it to no longer recognize the printer, and to keep adding more copies of the same printer, which often don't work either. I have noticed it adding synthetic copies of my printers for years (any type of printer - HP, Canon, Samsung, etc), but usually it was tolerable because I could just set one of the copies as the default printer and it would work. That strategy doesn't work anymore. I can't even use the synthetic copies of the printer now. One of the two things I didn't try the other day, plugging it into a different computer, was the answer. It works with Windows Vista and it works with Linux Mint. The printer is fine. The problem is Windows 10. Plugged it in and Linux Mint recognized it right away. No hassles with drivers or anything. The only issue was it wouldn't print an email until I rebooted the Linux PC and disconnected the printer for 60 seconds. I was hoping to get advice here on how to get Windows 10 to recognize the printer. I guess I'll just have to print from Linux from now on. Hard to believe Linux has become easier to work with than Windows, at least for printing.For most of us, substitution is the best way to test parts of out system.
Sometimes a problem becomes unstable and we can not find the fault.
I think the cable is failing. Also, if the power unit inside the printer has a small component failure, it will show that kind of trouble.
In any case, you have to try another printer and cable. The fault might be anything inside the printer, but my guess is the power unit, But that is only a guess.

Having a spare printer is a good idea. At local stores you can  cheap printers that are being sod as part of a promotion. I got one for under $30 and it came with ink.
Consider this: Ask a tech to solve the problem and he will ha veto charge you at least the cost of his time. In the developed world, it is more than cost of the promotional printer on sale.

BTW, all printers should have a removable USB cable.
The LaserJet 1200 is my spare printer. What I like about it is, laser cartridges don't dry out so you don't have to rush to use the ink within a short time. It's also fast, not complicated, no frills, and not fragile. I've gotten a lot of use out of it for more than 10 years and it's STILL going. I've also got a HP OfficeJet (uses ink) which is currently broken. It was fragile, complicated, and finicky. If I can't fix it I'll buy a new one. And if Windows 10 causes problems with a brand new printer, I'll just connect both printers to my Linux PC and use that as my main computer.Wait, I did not know you had a spare system.
So did you try the HP on the Linux system and it works OK?
If so that would indeed indicate the Windows 10 has got a problem.

When we suspect that Windows 10 has a hardware driver-issue, we try another install of Windows just to see. You can boot Windows 10 from a USB flash drive it will d find right driver for that printer.

Maybe you already know that, but for the all readers:
https://www.pcmag.com/how-to/how-to-run-windows-10-from-a-usb-drive

Microsoft offers its own tool called Windows to Go, which can generate a bootable Windows USB drive. However, that program works only with the Enterprise and Education versions of Windows 10 and requires a certified Windows to Go drive. A better (and free) option is a utility called WinToUSB, which can create a bootable drive from any version of the operating system and on any type of USB drive.

The article has some tips of how to do it. Having Windows on a stick is a big helpto find possible hardware issues.

That is the best I can offer. 
"When we suspect that Windows 10 has a hardware driver-issue, we try another install of Windows just to see. You can boot Windows 10 from a USB flash drive it will d find right driver for that printer."

But is that a permanent solution? It doesn't sound like it. It sounds like you'd have to shut down your PC and boot from the USB every time you wanted to print something. The link you included doesn't seem to indicate otherwise.

I had to print a receipt that was emailed to me. With Windows on a USB, I'd have had to shut down the PC, boot it with the USB, and then either install my email client on the USB or go to the webmail version. Even if the USB version of Windows found the printer and successfully completed the print job, I'd then have to boot it again to go back to normal Windows 10.
Completely reinstalling the printer would seem to be worth an attempt.

You would do this by unplugging the printer's USB cable, and uninstalling all Printer-related HP software and removing all the HP 1200 printers in "Printers and Scanners" (click it and then "remove device").

Once it's all gone, you want to first install HP's "DOT4" driver, found on the Laserjet 1200 page. Under "Driver-USB (1)" you want to download and install "HP LaserJet USB (DOT4) communication driver for Windows 8 and Higher (64-bit)".

Once that is installed- and still with the printer unplugged, install the Universal Printer driver available on that same page. Specifically, I'd suggest "HP Universal Print Driver for Windows PCL6 (64-bit)". During installation it should give you an option of different modes, from which you should choose "USB Mode Plug & Play". Once the driver finishes installing, you can then connect the printer and it should be detected and installed by the PC.