Can't login, not recognized


What is the problem?
I get a "User unknown or wrong password" error
What did you already try to solve it?
I saved my username and password in my password manager when I originally setup my Prusa i3 MK3 printer, I have never changed it.
Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)
This is a version of Octoprint called PrusaPrint. I set it up when I originally set up my printer, over a year ago. it is version OctoPrint 1.3.8 running on OctoPi 0.15.0PE

The window in my browser (Firefox) shows the progress of my prints, and the contents of my SD card.