Messages on my email server ( not showing up on K-9

I think I broke k-9 on my phone by trying to send myself a too-big file (yes, a video on my phone of my cat playing–should’ve used USB transfer, I know). After “sending” this, not only did the message not appear in my phone’s k-9 inbox or in its sent folder, but now I see none of the messages in my unified inbox from the past 4 days (all of which were there before I attempted that send, and all of which are available via the Sonic web interface and via Thunderbird). I’ve had syncing issues before and have tried everything–K-9 settings on my Google Pixel 7, Sonic settings, etc. Last time I had an issue with sent messages not showing in my Sent folder on my phone, I went to K-9 Mail: Settings: Sonic: Folders: Sent–and changed “Sent” from “Automatic:none” to “Sent.” Neither Sent nor Inbox are currently at “Automatic:none,” so that doesn’t seem to be the problem.
Any suggestions? Thank you!

Go to the “Outbox” folder and delete the message containing the large attachment. Then manually refresh the Unified Inbox.

Thanks for this suggestion! I deleted the offending message from my Outbox. This is embarrassing (shows how little I know), but when you say “manually refresh unified inbox,” do you mean just to swipe down from the top, as one would do to retrieve new messages? I’ve done that several times. I’ve received a couple of new messages from today after deleting that message, but all the messages between last Friday and today do not appear in my K-9 unified inbox.