Hm… not quite true… only enter password into API field into HA and it works. Currently i have latest 5.1.0 alpha FW and printer works flawlessly in HA. It also works with latest official 5.0.1.
Wow this means, that there is a security bug in the Firmware.
Agree - my MK4 xBuddy works fine with the device PrusaLink password only and v5.0.0 / v5.0.1 firmware.
Wrong API version number in PrusaLink for RaspberryPi was corrected Bump the api version to 2.0.0, so it's the same as the xBuddy one by TojikCZ · Pull Request #892 · prusa3d/Prusa-Link · GitHub 
Wait for next release or use master branch.
So I am still unable to auth against prusalink 0.7.2 using lastest HA OS. I’m running the hass container image and cannot figure out how to find the local files to try to debug.
Auth works fine when logging into the web interface (prusalink) but using HA, with same login get invalid auth. I have tried all combinations of user/password/maker/API key and nothing works. Worse I cannot figure out how to debug 
Could you be mixing up your credentials?
HASS uses local PrusaLink direct to my buddy MK4 board IPv4 address with:
- user
maker - pass
from the control panel
Works with the latest input shaper firmware (5.1.2+13478 and PrusaSlicer).
https://connect.prusa3d.com is for remote access only, and doesn’t work with HASS.
I think PrusaConnect shows the PrusaLink API key, which is the maker password for PrusaLink (and not the PrusaConnect Prusa Connect API key).
Confused? Yeah… I can see why…!
Yes, the fix should be coming in the next HA version: Bump pyprusalink to 2.1.1 and support Prusa MK3 by the-ress · Pull Request #114210 · home-assistant/core · GitHub
