Delays to Cloudflare Access "One-Time Pin" emails

Is there some known issue or cause for users not getting “One-Time Pin” email for Cloudflare Access in a timely manner. We have the sender addresses and hosts whitelisted in our mail gateways and simply aren’t seeing the email as even attempting connection for extended periods? Totally inconsistent as sometimes it seems message arrive very quickly and other times can take a good number of minutes; seem to then get utterly confused if a user tries to resend message, re-enter email address or close and reopen browser to restart entire process.

There doesn’t seem to be, according to

How long has it been going on? I haven’t tried lately using the One-Time PIN, but it has always worked instantly.