At the moment, Direct Debits are affected by this issue on Monzo. It is recommended that you don’t have them come out the same day that your salary (or other credit to cover them) comes in (don’t know if you remember, but you posted further up in this thread!):
And the issue was more recently confirmed, further down the thread:
Agree that this isn’t a good situation, hopefully sort it out before adding too many more current accounts. It’s the kind of little thing that could have big consequences for some people, especially with the charges and fees some payees have for missed direct debits.
And I agree that a simple ‘retry’ option for the failed standing orders would be great.