iMessage activation failed out of nowhere after restarting phone

I restarted my phone earlier because one app was acting up. When it booted up, a prompt that says "iMessage Activation Failed" just showed up, and under Settings it just says “Activation unsuccessful.” I can’t send or receive iMessages using my phone number.

I’ve already tried the usual troubleshooting: restart, reset network settings, etc., but nothing worked. I reached out to Apple Support, and all they did was direct me to submit a request through their form and wait 24 hours.

They suggested my number might’ve been flagged as spam, which is absurd. I only use iMessage with family. I'm very concerned because I read somewhere Apple can only unblock your number once... I've had this number for years and would absolutely hate replacing it. I would understand if I actually did something wrong, but I absolutely did not.

Has anyone else run into this? Any reliable workarounds?