@magicview 

I believe the issue is having the Deco X sitting behind the M9 so the cloud only recognizes the M9 or one Deco network.

You mentioned both SSIDs are available so with the Deco X wired to the M9 you were able to go in the Deco app and create a new network? (top left menu)

I think what you may need to do is to add the Deco X into the existing M9 network to be able to utilize all the units.

@Tony 

yes, with X60 behind M9, I can see both SSID from a device, I can also set two networks in the app (but sometimes the 2nd network withou internet access is automatically removed by the app).

if it's an issue with cloud access, then I don't understand why I could set M9 behind netgear orbi and have two working routers.

@magicview 

Both routers use different services/ports so I am thinking that may work.

If you were to run the X60 in AP mode does it get internet?

Also, since not getting internet to the X60, if you were to swap the M9 so the X60 (router mode) is now connected to the modem, does the X60 now have internet? You may need to reboot the modem to recognize the new router.

@Tony 

My interest is to set 2 mesh networks so I didn't try AP mode but I try it shortly.

I did try to swap X60 and M9, no matter which is connected to modem directly, the 2nd mesh network that connects to the 1st one always has no internet access (it seems the 2nd one is not recognized by the 1st network as I can't see it in the device list.