One of the first things I did with my brand new Pi 4 was to create a new user id for myself, and disable the login for PI. One of the second things I did was to try Mathematica (interesting, that is a spelling error here) and Wolfram and the Intro workbook "FirstCourseOnRPI.nb". The third thing I tried to do was run any of it, and I had absolutely no luck; I was consistently asked for a Key that I didn't have, and (in spite of several requests to Wolfram and this forum) was unable to obtain.
The problem was found in an old post here, which said membership in the group "video" was required. It didn't solve the problem at first, but after a PI reboot, all was well again. I (think, be careful, from memory) what I did was:
sudo chuser -a -G video myuserid (the capital G is important, to add(-a) a non-primary group (-G) membership for the user specified);
groups (to list memberships, find yourself and check video has been added)
sudo reboot (careful if on a vnc connection.)
The default user Pi probably wont have any of this grief, but at least change the default password!