e-filing amended return fails

[blmatthews]

I filed my 2021 return and it has been processed by the IRS, but I received a corrected 1099-DIV on April 21 (d'oh!), so I need to file a 1040-X. I stepped through the process, which at the end says to mail my return or click File to e-file. So clicked File, stepped through the e-file process, and when I click Transmit Returns Now, it finishes Reviewing and Preparing, but when it hits Validating, it fails with a reason of "cancelled / Looks like we've had a technical hiccup." What now?

[blmatthews]

Just installed the latest update and no change.

[fanfare]

@blmatthews 

When you amend on paper,

Do not include your old 1040 nor your revised 1040 because the Form 1040-X reflects any changes there and becomes your new tax return.

Include any new/corrected tax document only if it shows federal tax withheld, and include in order only those Sequence Numbered tax Forms and Schedules that changed or were added due to your amendment.
Attachment Sequence Number is on all the forms and Schedules that come after 1040.
Mail to the address shown for your location in the Instructions for Form 1040-X.

[blmatthews]

Thanks. I (paper) filed today, and did all that. I'm going to leave this open though, because the question isn't how to paper file, but why do I have to.