Please try this method and see if it works. If not, please respond in the comments here and I'll see what else I can find to assist you.
"How do I change from mail to e-file in TurboTax Online?"
https://ttlc.intuit.com/replies/5561257
NOTE: This was an issue earlier in the year, but was supposed to be resolved by now. Please let me know if you are still encountering the roadblock. Thank you for your patience.
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***