Ask the bank for new checks and let the other signers sign the check.

Or let one of the other signers withdraw from the account to obtain a bank check for the payment.

It is always difficult to know how to deal with an officer who takes a principled stand and refuses to go along with the majority opinion.  But an officer should not be in a position to stand in the way of the board’s consensus, particularly where, as it appears here, there is professional advice that the action must be taken.  If the treasurer is not willing to make payments when the rest of the leadership believes they are necessary, you might suggest that he resign if he is not willing to allow others to take the action.  If he persists in being an obstructionist, you might want to propose his removal from the office.  Normally the board has the right to remove an officer and sometimes it is necessary to invoke the power.