Log in security link email not being received

[tbutz (🏳️‍🌈 Producer of "low value commentary")]

I found this, which seems to have been a similar issue with icloud, although the “fix” is unclear:

Help

Hi I have tried to sign back into my Monzo app. Not getting the email link as icloud has decided not to work. Tried web portal but same issue. Ive emailed help but not getting their email as yep it’s my icloud email.