Internet not working on Tomato

Hello, I don't know if this is the right place to ask but I don't know where to do it...
I just bought a brand new Netgear R7000 and flashed it with tomato. Its connected to my isp router (according to my isp is not possible to connect it directly to the modem) The flashing process was ok but when I try to connect to the Internet on any device it fails. Tried both manual and DCHP configuration of the wan (in DHCP mode it gets correct ip) I also rebooted it, restore to defaults an re-flash it (tomato by shibby and Advanced Tomato) none worked.
I'm out of ideas, any help will be appreciated