I don't have a broad understanding Roth Backdoor conversions; I only know my own situation. What happened to me was that I had taken a distribution from my regular IRA, so that limited my ability to do the backdoor conversion. I finally figured out what was happening when I deleted my regular IRA distribution (which I had not had in previous years). Then I was able to go through the TurboTax screens. (In the end, I had to enter the regular IRA data, so I did not have a backdoor conversion.) Perhaps you have some other situation that prevents TurboTax from seeing the backdoor conversion as nontaxable.
I wish I could be more help.
Good luck!
