@EmmeBi61 

Hey Massimo

This could be that the AP is on a different subnet from the router.

When you connect directly to the router what is the IP address?    Compare this to the wireless IP address.   My feeling is the AP is handing out a DHCP address on a different subnet to the main router, that way you can connect wirelessly ok but it wont work

If this is the case change the IP address on the AP to match that of the router...   example ... router is 192.168.1.1    set AP as  192.168.1.2  

It might also be worth disabling the DHCP server on the AP and just letting the router hand out the addresses.

Hopefully this helps

@Philbert , thanks

Followig your advise I made one step forward.

Now I am able to connect to Internet through WIFI with my desktop and one mobile (on the good side).

On the wrong side:

- I am no more able to connect to internet with Ethernet cable

- Trying and connect another mobile, I encounter error "No IP addresses available"

Any hint?

@EmmeBi61 

Ok so it could be that your ISP Router doesnt have a DHCP..

Checking your currently connected device, what address are they getting and are they DHCP?   Do you know if your ISP router has a DHCP?   

If it doesnt turn on the DHCP on the AP but set the range to start at 192.168.1.3 onwards