The browser won't start
I'm using Ubuntu and when I start the vivaldi browser, it opens but it is just a blank white window. I can only close it by using the kill program command. It used to work but after I made a new theme in the settings it just froze and it hasn't started since.
Search the vivaldi profile dir
~/.config/vivaldi/Default/and delete the files:
You may have a problem with GPU
Try start vivaldi with
vivaldi --disable-gpuin Terminal