Disable all addons which suppress lua error messages and try agin, see if you get any ingame lua error message as you open the addon settings (LibAddonMenu (LAM) 2.0). BugCatcher, NoThankYou, and similar ones.
I guess there is some addon which breaks it for you then.
And please read this to strip old/outdated versions of LAM 2.0 from any addon's subfolder "libs/LibAddonMenu-2.0") you are using:
https://www.esoui.com/forums/showthread.php?t=9335
https://www.esoui.com/forums/showthread.php?t=9420