Ok so Voided and Cancelled checks are 2 different things.
a) Only unposted checks can be voided---- then reused
b) Cancelled means check has been posted and you used the reversal option from the cash & bank module to reverse the payment. Release the invoice and forget about that check number.
It is impossible to reuse the same check number (even if the parameter Reuse check number is ON) after it has been posted and/or reversed.
To use correctly the reuse functionality you must create a payment journal, generate check, before posting it is possible to 'Reject' the check and start over. With the option of 'Reuse numbers' in the drop down of the payment status in the payment journal, you will have access to a new status which is 'Reuse'.
This option of reusing check numbers is only available before posting the payment journal for compliance purposes as always.