[Uptime] Uptime not sending emails when site is down

Our site is down today and I would have expected a notification email from WPMU DEV's Uptime Monitoring. But no emails were sent to me. I have made sure that I'm checking the correct email address and I've also checked spam and junk folders.
I've made sure "Email Notifications" is turned on in Uptime settings in the Hub. I have also tried restarting Uptime monitoring, which didn't help. Is there any way you can check if they are being bounced your end?