Hello,
My wireless router works when plugged into the Cable modem, I then added a gateway between and it worked for a while but now I can get internet via the gateway but the wireless is not getting to the internet
modem = ubee
gateway = Linksys switch (which is different than a gateway)
router = Netgear router (which has the gateway)
your modem will only give out one IP; therefore, the switch needs to be connected behind the router so you can have two or more devices connecting to the internet at the same time.
You know your router also has a built-in switch so you can use it for both. Are you adding the switch because you need more ports to connect to the router?
with the devices you have right now and to get everything to work in the office and upstairs, you will need to connect the router to the modem in the office and connect the switch upstairs.
are you trying to keep the office separate from the upstairs? If so you will need a second router.