Have you followed the instructions that can be found in the official support pages to install Plasma? Installing a different DE in Pop (or any other distro that comes with a DE preinstalled) isn’t so simple. You may want to test if the problem persists if you login with a brand new user, if not then it means that something in ~/.config is probably broken.
Of course that's why they had so many new accounts so fast! And that's why removing the Threads account also deletes your Instagram one! No way a bad app like that, missing the basic features (front what I've read in reviews), would have so many users so fast!
Does it work in the login screen?
Have you followed the instructions that can be found in the official support pages to install Plasma? Installing a different DE in Pop (or any other distro that comes with a DE preinstalled) isn’t so simple. You may want to test if the problem persists if you login with a brand new user, if not then it means that something in ~/.config is probably broken.