How do I get CiviXero to add a specific contribution to it's account_invoice table for consideration?
I think if you just edit and save the contribution, it should be added to this table (provided it does not end up with any error).
How do I get CiviXero to process a specific contribution. I've tried invoice push job with contribution_id as the argument. ...
It seems to be an issue with xero (I'm assuming it's an extension/plugin that you have enabled on your site)?
If you are using fuzion's extension, you might want to check if it's already logged as an issue or if there is a solution already