EDIT: SOLVED! It was a server malfunction. From tech support's message to me: "The error was caused by a problem with the temporary storage area on the server. That area had developed an internal error that forced it into a read-only state, which stopped MySQL from creating the temporary files it needs and made the database tools and WordPress login fail.

We fixed it by rebuilding that temporary storage area, setting the correct permissions, and restarting the database service."

Everyone had great advice, and I'll certainly use it all as reference if something similar happens in the future. I've already reset allllllll the passwords and am running scans just in case. But I was able to log in as soon as they made those repairs. The menu reappeared after I deactivated it and then reactivated it again.

Thanks again for all of your help! OP folllows.

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Hello all, client messaged to let me know that the site menu is missing. I try to log in at the dashboard and can't: incorrect password. Reset link doesn't work. Updating password in phpMyAdmin doesn't work. Password update in cPanel > Wordpress Manager doesn't work. Hosting company tries phpMyAdmin password reset on their end. It doesn't work.

I did have to deactivate Jetpack because that ridiculous math captcha kept throwing an error. I hadn't set the ridiculous math captcha, and haven't seen since I turned it off a couple of years ago. But it was there today. Logs show an update for Jetpack was found on the 16th but I don't have auto-update on for Jetpack bc it always *borks* something. So the update wasn't applied.

Another clue, maybe? Each failed login attempt returns an error message that states 4 login attempts remain. Host's tech support say that's part of the Defender plugin, so I deactivated it. Next failed attempt: 4 remaining.

== EDIT: The host found the Defender script was still running despite me deactivating the plugin so they stopped it. The '4 remaining' message is now gone, but I still can't log in. Remainder of OP follows. ==

I've gone through our files and nothing looks off. No additional users showing in phpMyAdmin. No new pages/content on the site (although the menu is still missing). I'm stumped.

Any ideas?