Then I suspect the GL side of things are still expecting everything to be on :51820. You may need to get into SSH &/or LuCI to make some customizations. Before you do I'd revert your latest change, then pull a backup:
I'd poke around /etc/config/firewall, /etc/config/network & /etc/config/wireguard_server (that last one is GL.iNet specific & not found on stock/pure OWRT).
/etc/init.d/firewall restart && /etc/initd.d/network restart should be executed to make any changes you've made effective.