I had this yesterday for a small time change, no flight number change.
I called up, and spoke to a very helpful and friendly agent in Trinidad.
She said there was no issue with the seat map on her computer although I could only see the greyed out version with my seat showing online and on the app.
After the call everything working fine.
(I'm impressed with the pictures @
donotblink. I must take the time to learn how to do that!)