Without the WireGuard server running, the firewall of GL-MV1000 blocks access from the WAN even on your own network.
To access the GL.iNet Admin Panel from your own network, you have to open the firewall:
I prefer to Port Forward WAN TCP Port 80 to LAN IP 192.168.8.1 (or whatever you have set up) TCP Port 80. You can also just Open Port TCP 80.
I do not work for and I am not directly associated with GL.iNet