I'm having a similar issue where I can not send my invoices. I get an error box that pops up and says Unrecoverable Error.  After searching around, I went to Preferences and Send Form and the minute i click on it, I get the same Unrecoverable Error box. So it appears to have  something to do with sending forms. I've upgraded from Quickbooks Desktop Pro Plus 2023 to 2024 and ran several updates and nothing has changed it.  Any suggestions what else to try?