cannot connect to wan router

[ciocchi]

hi everybody
I use a tplink wr841 as router, connected to wan via tplink modem/router wa901 (3g usb). I can navigate in web and see the server at 192.168.0.10 but I cannot see the modem/router at 192.168.0.1.
see the page attached.
what's the trouble about it? thanks

[ispyisail]

the routers need to be on different subnets?

e.g.

192.168.0.x (router 1)

192.168.1.x (router 2)