Sorry, it’s so long (years) since I posted a cheque to Monzo, I don’t even know if you get a notification or if the first thing you know is when it clears and is credited to your account.
I think most people on the forum who get cheques regularly would keep a second account with a legacy bank for that purpose - we do, to avoid this issue.
Sorry that’s not much help but maybe another forum user can advise. In theory they have another week at least (possibly more if the two weeks is from receipt of the cheque) but hopefully you see the money soon.