Try unplugging the Beam from power for about a minute and rebooting your router. If that doesn’t work, you can try connecting the Beam directly to the router with an ethernet cable.

There are so many situations that could cause this to occur. I assume you can’t run an ethernet cable from your Beam to your router. If you have any other Sonos speak with ethernet port near your router you could hard wire that one and the other speakers will create their own mess network which could help. Failing that you could try the Sonos Boost. 

Thank you, i will try to hook it up to the ethernet cable and see if that works.

However, don't use a surround speaker or a Sub, it essentially needs to be a ‘primary’ speaker.