You cannot defer self-employment taxes if it is going to result in a refund. Even though the refund is from the amend, the software caught the deferral, sees a refund and now disallows it.
You cannot go back and say you aren't deferring the self employment tax either, because you already did defer it.
If you take the self employment taxes you could have been subject to in 2020, you probably would not be owed a refund with this amend anyway.
Try to print out the 1040X after you make the amend. If you can print it, then just mail it out.
If not, I would suggest contacting the IRS and seeing what can be done. You are deserved of whatever refund resulted from the additions you made, because the self employment tax would be paid eventually if not already.
