I am having the same issue many other users appear to be experiencing. I have read multiple forum posts on here with no resolution. I am creating one to try and resolve this finally.
Flight from EGLL to OMDB. Unable to enter values into MCDU with error “NOT IN DATABASE”.
I have attempted reinstalls, verified an regenerated configuration.xml all with no impact. The lack of logging is honestly disgusting from Microsoft so I feel some of your pain.
If I could get some help as a paying customer that would be fantastic.