Unable to e-file amended 1040X for 2021

I've prepared an amended 1040X return in TT (download/desktop version), but when I try to e-file it, TT says "it looks like you haven't e-filed your 1040 through TT" and  won't let me e-file the 1040X. But I did e-file my 1040 with the same version of TT, just two weeks ago; I was careful not to download any updates to TT since then and am using the same version that I prepared and e-filed my return with. Why doesn't it see my record of e-filing and how do I fix this so I can e-file my 1040X?