Amending a 2023 return - all Old Amounts show as $0

After e-filing, I tried to use the Amend and ReFile feature in Home & Business - downloaded edition on Windows 11.  

Choosing the ReFile for my 2023 return (on the NetFile page), it then led me through all of the profile questions and Easy Step sections.   BUT when I got to the Summary for ReFile it shows ALL of the Old Amounts as $0, not the originally filed amounts.  Switching to Forms mode, I can see that the RSUM form is showing all the old amounts as $0 and the Changed Amounts as the new calculation values.

 

I cannot change the RSUM info manually.  How do I get it to undo all this and go back to the as-filed information, so that I can try to Amend the return again?  Or am I stuck now and have to amend this using the CRA Online adjustment form (but TurboTax suggests I should not do this for a NetFiled return).

 

Sadly I do not have an archived version of the tt23 file from before making the amendment (my bad I guess, but it asked me to save and I was clicking along merrily).