Adagio uses the word "void" to mean the check never printed properly. You want to use the word "reverse".

You reverse a check under Check Reconciliation and then post the reconciliation. The default is to re-establish the invoice(s) as payable, for the check to be re-issued. If you don't want to re-issue the check, then you will need to enter credit note(s).

There are some special circumstances when you can credit the invoice at the same time you reverse the check, but for a beginner like you, just stick to the default settings.