What is the problem?
Display Progress plugin installs but HD44780 20x4 lcd not showing anything(line 1 and 3 display rectangles.
What did you already try to solve it?
ran test.py script and the display works correclty. the constrast of the display is set correctly.
Have you tried running in safe mode?
Did running in safe mode solve the problem?
You can download this in OctoPrint's System Information dialog ... no bundle, no support!)
Additional information about your setup
OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible
Octoprint 1.8.6, OctoPI 0.18.0, Virtual printer(will use Anycubic Vyper), browser - Google Chrome.