Sorry for the late reply
I just tried Brave in my personal machine and it seems to be working (installed through flatpak)
What extension specifically are you trying to install? And what distro do you use?
EDIT: Just noticed its Bitwarden you want to install. And this one also seems to be working fine. Maybe you could try to reset Brave? You do it by deleting the folder /.var/app/com.brave.Browser/ in home. But be careful because you lose all your browser data by doing it.
Good to hear, and best of luck with your computer :)