Try a different browser and that will answer your question. Everyone has backup browsers on the computer.
If it logs on, then you have to use the previous version of Firefox.
To see what version you are, Click the three bars on top right and go second from the bottom. Help>About Firefox and it will tell you what version you have.
Uninstall the old one and install the previous version.
Shut off updating or it will put you back where you began.