You need to include the files in the zone file. Bind 9.18.18 is a mess with the changed DNSSEC setup, it broke my domains as well. I’t isn the bind documentation, so I have to refer you there. I have no access to my setup now (or my browser history) as I’m not at my computer.
Edit: managed to get in dns.
named.conf.local: zonefile needa to be the .signed file the unsigned zone file must have both keys included, best is via absolute path: