RoyalTSX > Check for updates...
Plugin Updates (only if there are plugin updates) pops up. Update all button cannot be clicked. Found out that there is another popup exactly behind the plugin updates popup called "You are up-to-date".
Work-a-round: move the plugin updates popup aside and click OK on the other popup called "You are up-to-date".
this will be fixed in the next minor update.
a beta version which includes the fix is now available.
Hope that helps!