That might work. Perhaps if client used another program like Turbotax, selecting self prepared might allow the amended selection to pop-up when efiling.

I broke down the steps I took, but this is really for clients you might have already done an original return for, as well as an amended return, but can't seem to efile the amended. I wish we could edit replies instead of reposting. 

Solution:

a) Once you receive a 'Rejected' status from the IRS, click to open the amended file, and UNCHECK the "efile federal return" box, just under Part VI (It's ABOVE the box of states that can be efiled).

b) Do the final reviews, click "File Electronically" on the left sidebar as if you were normally efiling. 3 rows will show up (fed amend, state, and state amend). The box next to "Federal amended return" should now be available to select. Select it, and efile that one only. Because you unchecked the "efile federal return" box, this efile attempt will fail (which is what you want) when you attempt it because the program won't allow this error to pass. 

c) Once you get that failure status box, open back up the same amended return, CHECK "efile federal return" (under PART VI), go through the final reviews, and efile like normal. THIS time, when you go to efile all 4 rows will appear (fed, fed amend, state, state amend).

d) Select box next to federal and/or state amended return, and efile as normal.