In general, once a voucher has expired it can no longer be used.
If you've missed the expiry date of a voucher, you're welcome to ask the venue nicely if they might still be able to accept it. Please just keep in mind this may not be possible and the venue isn't under any obligation. If they can't, we're really sorry to say your voucher will be considered forfeit.
If you ever find yourself unable to use a voucher before it expires, you could always gift it to a friend or family member so they can enjoy it instead.