iPad and iPhone loosing Sonos speakers

[Storah]

I am having problems with Sonos and Spotify.

I have some Sonos speakers that keep disappearing from the Spotify app from my iOS iPad and iPhone but they are visible on my iMac.

I have deleted the applications Spotify and Sonos from both devices and rebooted them both but still they do not appear.

If I reboot the speakers themselves they appear for a short period of time but then disappear again.

This can not be a Sonos problem as the speakers work fine in the Sonos app and they also work ok in the Spotify app on the iMac. It’s just on iPad and iPhone. Both iPad and iPhone are running 13.2.3. 

This problem has been ongoing for months. Can someone please advise me how I can fix this?

Thank you.

[Storah]

Anyone?