Mouse not working in Vivaldi only
Weirdly, when I went to use Vivaldi today (Nov 13 2017) in Ubuntu 17.10, the mouse buttons do not work at all. I did fiddle with th the Settings earlier, and may have turned off mouse gestures, but I can't do a thing in Vivaldi now without the mouse. Quite strange!
Please open Vivaldi settings
and reset Mouse gestures
and reset keyboard settings to Default.
If that does not help backup and reset your Vivaldi profile.