Monzo payment requests aren’t going through instantly. Takes more than a day for the other person to receive. Did not happen befotr.
Presumingly we’re taking about Faster Payments here, these are normally instant but can take up to 24 hours to be received on a slow day, sometimes even longer if the receiving bank holds it for whatever reason unfortunately there isn’t anyway to change this but hopefully you should see it go back to be instant sooner rather than later!!