Omnigraffle Visio files on MAC

I’m having difficulty viewing visio files on my mac in omnigraffle - in particular these are IVR call flows.

Any table or similar item has been turned into a large gray square. I am also not able to click on any of the navigational items to push me to the appropriate page. None of these items seem to be active.

Since i am new to Omnigraffle, it’s possible that I have not enabled something or simply don’t know what i’m doing…but i’d appreciate any help you can provide!