502CR has been an issue for many years. Required to be e-filed, but the MD502 doesn't support the line for the credit. I tried overriding it and it failed e-file, even with turning off the error check.

I complained to ProSeries and the Comptroller of MD.  Their basic answer was to buy another software that supported the line.  So I tried a Pay Per Return Lacerte and that failed too.

I contacted the Comptroller (the prior one) and his assistant told me to mail in the return stating the issue and asking for an exclusion to e-file.  For 5+ years this method did work, even though it was slow to be processed.

I also did a request for software update for many years and P.S. ignored it. Not enough people were complaining.