Mail doesn't send and just disappears
When I send an email (Gmail) from my Mac desktop, it sometimes just disappears and doesn't send. I can't find or recover it anywhere. Not in sent mail, nor my inbox (I bcc myself on all mail) nor in drafts, all mail, nor archive. No outbox shows either, and no notice that it didn't send.
I only have one email account for personal use, and never had problems previously. If something didn't send, I used to get a notice of a failure, and given options. There was always then an outbox that showed up, where I could find the email. That's no longer happening.
Thanks for any suggestions.
iMac 27″, macOS 12.0