Object reference not set to an instance of an object error

I am working on a diagram which is stored in Modeler Services and when I try to open it, I get the Object reference not set to an instance of an object error message and I cannot open the diagram.

I had this problem earlier, and am apparently stuck with a diagram that I cannot open, and cannot delete from the folder. I decided to just start over from scratch, and now the replacement diagram has the same issue and I cannot open it.

Bizagi is becoming unusable to me. In searching, I find reference to this same error on postings 4 years ago. Is there someone I can talk to?