If a check is issued to John and Jane Doe, the check is payable to all payees. It must be endorsed and negotiated by all of them.
If a check is issued to John or Jane Doe, the check is payable to each payee. It may be endorsed and negotiated by any or all of them.
If the check is unclear as to whether it is payable to both payees or just one payee—such as being payable to John and/or Jane Doe—then the check is payable to each payee. It may be endorsed and negotiated by any or all of them.
A checking account may be established with only one signature or with more than one signature on the signature card.
If only one signature is required, any one person may legally withdraw all the funds or close the account. If two or more individual signatures are required, but the bank cashes the check or closes the account without the proper number of signatures, the bank may be liable for the amount of the loss.
Contact the bank directly and notify them of the situation.
Because you are not the maker or the endorser, this is considered a third party check.
A national bank sets its own policy to accept or reject third-party checks. If the bank accepts the check, the bank can require the payee to be present to verify the signature.
There is no law that requires a bank to accept third-party checks.