I too had the exact same rejection code: F1040X-007-01
I found a forum on reddit (https://www.reddit.com/r/tax/comments/me0ud0/rejected_amended_return_1040x/) where several people have resolved this issue *BUT* only if they used the free online version!
I bought the TurboTax Deluxe Mac edition, and the issue cannot be resolved the same way. It appears that the problem is that Form 1040-X, Line 7 (which reads 0. 0. 0. for me) does not match Form 1040, Line 21 (which is BLANK for me). The sections that should be filling in the latter as 0. (instead of a blank) won't update this field and thus the IRS e-file system rejects my amended return on the grounds that these numbers are not equal.
Hopefully TurboTax support will help us out soon, but if not it seems the solution is to give up on the non-free versions of TurboTax. My current best bet is to use the free online edition and go (Step 1) REDO your entire 2020 tax returns matching the erroneous, pre-amended values, then (Step 2) REDO your amended version using the online system.
Help us, TurboTax! Please! A lot of us have big $ (for us) on the line because of the various stimulus checks!
