I hope this will help you to join your Friend because it's frustrating if you can't, Right?
Make sure you and your friend/s are in the same area, same area I mean you're connected to either same wifi or hotspot. If you are a Data User, The Host should open their "Use Cellular Data" and he/she should be the one to open their hotspot, Where to find it? Go to Settings then press Profile, Whaaaa That's it?? Yes
I don't have editing skills so, you can turn off your Volume if you want too, That's it, Keep Safe!! ^^