Instead of going through the WireGuard client on your Creta router, can you do a test using a (free) WireGuard client on your laptop to connect to the WireGuard server directly and try accessing the GL-MT2500 admin page?

With a WireGuard client on my laptop, I can access the admin page of my GL-MT2500 at its 192.168.x.y LAN IP address. If this works for you also, then the issue only relates to going through the Creta.