I'm a fellow user--not a tax expert--but I know how how some filers have handled that in the past if you have the following scenario:
Did you report your foreign earned income, then used the Foreign Earned Income Exclusion (Form 2555) to exclude all of your income, so you ended up with a zero-income return? Although you cannot efile a zero-income return, there is a workaround. I have seen some filers in this forum simply add $1 in interest income which should allow the return to be efiled. Or one guy said he reported $1 in "Other Income", and for the adjacent explanation said "in order to efile."
If you need additional info, report back and hopefully, someone more familiar with the Foreign Earned Income topic will join in the discussion.