I'm a California filer and was trying to resolve the "No ECN" error when I was eFiling.
Open your return and navigate to the following section.
State Taxes -> Continue -> Edit -> Credits and Taxes -> Health Insurance Penalty -> Revisit
Q. Did you all have insurance coverage in 2021?
A. "None of us had it at any point" << this was my selection >>
If you answered like this to the question about insurance and clicked continue, then the next screen is very important and related to the error during eFile. It's not a TurboTax bug per se, it's in how the state prepared the forms and it's easy to miss some important clarifying text on the TurboTax screen.
Click <CONTINUE> once you've answered the "Did you all have insurance coverage in 2021?"
The 4 groups of checkboxes on the next screen are important and related to the issue.
If you checked ANY of the boxes in the 2nd group ("Exemptions granted by the Marketplace (Requires an Exemption Certificate Number)" - you will have this issue. I had incorrectly checked the "Coverage was considered unaffordable" which was the issue. I removed this checkbox and continued through the rest of the sections and after TurboTax performed the required calculation, I was still eligible for a waiver to eliminate the "Shared Responsibility Payment" and I was also able to eFile with the "No ECN" selection in my 3853.
This is not tax advice - this was my solution to the problem that so many seem to be struggling with.
Good Luck
