Update: As I work with both QBO and the competition software which shall remain unnamed, I encountered the same problem there. BUT, there, the community members have already sussed out how to solve the issue.
The issue is that the CRA as of this year wants to see your Rep ID, which is the 7-character alphanumeric code you see in the top right beside your name when you log into the CRA website. The top of that xml file needs to be amended. Here's what the top part of the T619 record looks like in the other software:
<T619>
<TransmitterAccountNumber/>
<TransmitterRepID>
</TransmitterRepID>
<sbmt_ref_id>XXXXXXXX</sbmt_ref_id>
where <RepID>CCCCCCC</RepID> needs to be your 7-character CRA rep ID, visible in the top right beside your name when you log into the CRA site
IMPORTANT: You must keep the capitalization on your Rep ID and you must respect the indentation as shown. I just tested it with my one QBO client and it all went without a hitch.
So edit your XML file, add the above lines right under the first T619 before the sbmt_ref_id and you should be golden.
