I found many related articles on this, but the details of my situation don't seem to line up with the common queries.
I have a VF Page that I want to pull information from via the current account. So, the controller is an Apex class that gets all of that.
When I try to use this VF Page for the button (trying both Detail and List Button), it does not appear.
StandardListController = "AccountRenewal" (that's the .apxc)
'Unsupported attribute standardListController in in AccountRenewal at line 1'
No standard controller was specified - recordSetVar cannot be used.
I try then adding
StandardController="AccountRenewal" alongside that to appease it, but since that's my apex class, not a standard controller, it says it does not exist.