I have an airport extreme as my main WIFI router and I have an Airport Express downstairs which is set to extend the network and it works flawlessly. I recently also got a second Airport Express to extend the Airport Extreme network at my top floor and it always tells me it cannot join the network with the exact same settings as the other Airport Express. At the location where the upstairs Airport Express is set up, the network signal strength is good.
My question is: Is it even possible to extend an Airport Extreme network twice with two different Airport Express routers, or is this not supported?