Airport Express disabled wifi network?

I took my new Airport Express to my brother's house to see if it helped to extend his wifi signal (he is in a rural area with lousy internet signal). Connected AX to his modem using ethernet cable, using WAN port on AX. It never would successfully start up. Tried multiple times to re-start AX with no success. I had Airport Utility app on my iPhone 5 open but never detected the AX. Gave up trying after 1-1/2 hrs of effort. NOW, my brothers wifi is out completely, apparently since we disconnected the AX. Did the AX cause his outage or is this coincidental? Did multiple re-start attempts throw things out of whack? I'm feeling guilty for taking the AX to his house, fear his modem is broken and it may be the fault of the AX. Would appreciate any thoughts....