Norton INTERNET security - NOT WORKING?

Hi, everything was working fine and I hadnt noticed NIS had stopped running until today, whenver I try to open the program or perform any kind of scan, nothing happens or i get this message 

 

 "c:\program files (x86)\Norton Internet Security\Engine64\19.7.1.5\uistub.exe"

 

Does anybody know what this is...and how to fix it??

 

Cheers for any help or advice.

 

Thanks