ladybugfruit,
I'll assume you are talking about the plastic expansion joints. If these are cracked and/or broken, the best way to solve is to cut the expansion out and fill with Deck-o-seal or some similar elastic joint compound.
It's a pain to do. Haven't looked recently to see if anyone makes a glue on piece for repairs.

Thanks for the response golfgeek. Yes,it is the plastic expansion joints and they did get cracked. So basically, it would be replaced with the same material that is used to replace the mastic? That was the only thing we haven't done yet with the pool remodel. Guess we will do it all at once now.Any problem with waiting til fall to do this? Thanks so much!

ladybugfruit,
Yes, same mastic. Shouldn't be a problem waiting until fall.