Is this failure with logging into websites or with Brave Browser itself?
most likely if it is with the Browser your Keyring probably got corrupted somehow
with the browser closed navigate to /home/username/.local/share/keyrings/ - where "username" is Your user name - you will need to have Show Hidden Files checked to see this folder - to do that open your file browser Nemo in your case and click on View then put a check mark in "Show Hidden Files" now you should see the .local folder - any folder with . in front of it is usually a hidden folder
the photo is from my system which is Xfce and Thunar for the file manager but it is similar to nemo - on mine you can see Default_Keyring.keyring - yours a maybe little different - the point is open it and read it so to make sure you have the correct keyring - now just delete that file and go back to the View and uncheck "Show Hidden File" and close nemo
View attachment 32500
Now open Brave Browser - you will get a box popup that wants you to put in a password - leave this blank on both lines and click continue the next screen will popup just click continue - now Brave Browser should not ask for Authentication anymore