cannot update citation

When I try to put a citation, it comes as an unformatted citations like this:

{Scanlon, 1991 #331}  

When I click ‘Update citation and Bibliography’ it says, ‘Cannot edit Range’ !!!

What I can I do? PLEASE HELP ME! Feeling helpless…

Is there any chance that you might have installed Mendeley at some point? All of my searches point to that:

If you have Mendeley installed on same computer. Open Mendeley > Tools > “Turn off Word CWYW add-in”.

I had the same issue
Thanks for the help