The user in which I installed the Mathematica is removed. There I could launch Mathematica by double-clicking its icon as well as any .nb file.
Now that I'm in a new user, for some reason the Mathematica icon is not even in the Application menu and double-clicking .nb file returns "Could not display 'xxx.nb'." and asks me to search online the software to link .nb file, which brings me nowhere.
I can still launch Mathematica via terminal command "math" or "mathematica" etc., but I wish I could just double-click launch from the desktop environment.
Debian 11 + gnome 3.38.6