The contract isn't ready to be validated until all the signers have signed.
You may have put several signers, thinking that the others would simply be copied.

It is therefore necessary either to bring the additional signers to sign (you can relaunch them from the current contracts), or to resume this contract and delete the additional signers, then have it signed again by the first signer.

To do this, from the front office choose the same customer, and in the transaction history click on "Resume", then on "Resume" in the dialog box which requests confirmation to re-open the transaction.