IRS rejected my return due to Code B on a 1099R. It does have a code B. What do I do?

Code B is a valid distribution code for a designated Roth account. May I assume that the account you took the distribution from was a Roth account?

Was this a Roth account that was created at least 5 years ago? Are you at least 59 1/2?

What was the IRS reject code?