Not sure how you could have gotten Line 8a checked for "Yes" but there's no input for Line 8b.  The reason is that ProConnect Tax defaults the response to "No" unless you make any entry on the line City and country of separate foreign residence if maintained due to adverse living conditions (if applicable) (Click on button to expand), in which case, you'd have "Yes" for Line 8a with the corresponding response for Line 8b.

I would have thought there's a critical diagnostic if anything is amiss for this line, so you shouldn't even have been able to e-file without clearing the diagnostic or checking the box to ignore it.

Suggest you check your input again.