Hello and Welcome to the Community, email11 :party_popper:
We can help get to make sure you're able to send this submission to HMRC - firstly, please check that you have the correct UTR no., Employer’s PAYE reference no., and Accounts Office reference no. entered within your CIS profile (Cogwheel > Account & settings > Advanced > CIS). Please get back to us below once you've checked that these are correct and are not causing a failure with the submission. :)