I am an executor. in filing form 1310, turbotax indicates that if i select part 1, box b, can't be efiled. IRS instructions show otherwise?

You cannot attach the court certificate in the program so you have to print and mail the return.

i already provided the court certificate, so that isn't being provided here.

I believe the program still "thinks" it needs to be attached. 

If the programs indicates it can't be e-filed, then you have to print and mail.

If Part I-B is checked, then the program would likely force one down the 'paper' path and e-file would not be an option.

However, in those cases where there is NOT a court appointed personal representative (e.g., Part I-C checked and Part II-1 is YES and Part II-2a&b are NO), then TT will allow e-filing.