A setup debit instruction seems to be cancelled from your end. The company has said I should get in touch, do you can accept the instruction.
You need to speak to the merchant to understand what they are asking.
Direct debits are generally only cancelled by you or them, not monzo. This can happen if payments have failed multiple times.
It’s also worth adding this a community forum, if you need to speak to Monzo use the in-app help and contact options.