[fireworks]

"I discussed this with our backend team and upon deeper investigation, we were able to confirm that there was some issue sending the notifications to your email."

Nope.

[dboreham]

Guesses 1, 2 and 3 are : their MTA's IP was black listed by a reputable mail hosting provider's spam filtering system (because they send spam).

[joemi]

That phrasing doesn't rule out an issue on your email server's end, like the email could have bounced. (Though I'm guessing that's unlikely.)

[fireworks]

Would be surprised if that was this case - vanilla GSuite setup.