Try rebooting your router and phone.

If you are trying to Bond it into a surround setup, not Group, you can’t Bond just one surround to a Beam/Ray/Arc you must have two matched Sonos to get the Surround option to enable.

@GillianinPS 

You should be able to group your two Sonos rooms (Beam & OneSL) held in the same Sonos Household/System using the method described in this Sonos support link:

https://support.sonos.com/en-us/article/group-and-ungroup-rooms

Note though you can’t create a saved Sonos Group in the App unless you have 3, or more, Sonos products. Neither can you ‘bond’ (not group) a single speaker to a Sonos Beam to use as a Home Theatre rear-channel surround speaker.. that requires two compatible speakers, rather than one, for the rear left/right channels, as outlined here:

https://support.sonos.com/en-us/article/surround-sound-guidelines-and-limitations