When I try to link up my Shutterstock account to my facebook account to do the autoposts about my sales, I get an odd error message:

I've gone through this with SS support and we've exhausted all possible explanations - am wondering if others have had this issue and if so, how they solved it.
I've tried:
1. deauthorising the shutterstock app from publishing to my profile ie: completely deleted it within facebook; then re-connecting it
2. adding it to a different facebook account (same outcome)
I've also tried option 1 whereby I've selectively enabled options for the app, but with no change in the outcome.
Only other option available that I can see is to set up a new SS account and start again, though that seems somewhat drastic...