"Looks like there's a problem with your game" - Scanning game files/"updating"

I have been trying to “update” WoW for at least 5 hours.
The blue button says UPDATE instead of PLAY, so I click it. It acts like it’s initializing an update and then says there was a problem and they need to scan all of my game files.
“Give us a few minutes to finish this scan” is, at this point, a cruel joke. I’ve been waiting for 5 hours for it to finish this. Every time it scans all of them, it goes to initialize the update and repeats the scanning process. I’ve restarted my computer. I’ve restarted the launcher. I don’t know what else to do. I guess my next stop is uninstalling and reinstalling the launcher. If that doesn’t work, does that mean I have to completely reinstall the game itself? Jeez, that’ll take me a whole day at least. I’ve submitted a ticket. Estimated wait time is 24 hours, so I’m here to see if anyone else is experiencing this or if I’m just SOL.
Thanks in advance.

2 seconds before hitting the post button: Hmm… it just said “starting repair” which I don’t think I’d seen before, but now it says “Scanning game files”, yet again. I won’t hold my breath.

I should mention that this is not Classic, but Retail. For some reason, it automatically chose the one character I’ve made on Classic as my default.
Also, the “starting repair” was a false alert. It’s still looping this nonsense.