Magic Mouse trouble

[Airey type]

Suddenly I can't open files with a left double-click though right clicking brings up "open" OK. ?Any ideas

 

[Cory Cooper]

Hello and welcome.

-Which model Mac?
-Which version of OS X/macOS?
-Have you checked the settings in  > System Preferences... > Mouse > Point & Click?
-Have you tried a simple restart of the Mac?

C