I read something recently where there were 2 related families (2 generations) living next door to each other and sharing WiFi. The mother, I think it was, had the windows in her house replaced with modern ones that had all the UV coatings, etc. on them and from that point on couldn't share the WiFi.
Moral of that story is that maybe the gazebo windows are blocking the signal. Try opening the windows and see if you have any better luck.