Sonos Boost trouble shooting

I have a new Sonos Play 5, which is in the gym extension. My wifi does not go to that area too well, so added a Sonos boost closer to the gym. However, after setting it all up, whenever i go into the gym, the Sonos app defaults to 'You need to be connected to a wifi network' message.

How do I test the Boost signal, or see it I am connecting to my network, through it, or if the PLay 5 is connecting to the boost??? This is really frustrating. I am using an iPhone 7+. When i do a WiFi sarch, it just sees my hub, not the boost?

I thought Sonos was suposed to 'just work'!!

Please help.