Process builder doesn't show all objects

I tried to use the process builder to create a workflow to update a field in Opportunities but Opportunities doesn't show up in the list of available tables on which to build the process. We use Click and Pledge for donation processing and that system adds a TON of custom objects. The system stops displaying objects after the C&P tables (C&P Widgets is the last item on the list). It's as if it truncates after some number of tables. I feel like I've encountered this before but can't recall what I did to get around it. Anyone have suggestions? I'll use workflows if I have to but trying to move to Process Builder for all such tasks.