P6 Professional 16.1 will not add new pred or succ in Window but will using highlight and button combo. It is almost as if something is keeping the add activity window from popping up. I will pop up if I click an existing predecessor and change it but will not if there are no predecessors. Same with successors. I can work around not being able to just simple add a new predecessor by just using the activity above it using highlighting and the top ribbon button and then change it - but I assume this is a bug or something. I made sure I allowed popups, at least I thougtht I did in the correct spot. Odd thing is that it has worked fine for a year. Any ideas?