Crossfade not working?

[JenBot]

Plan

Premium

Country

 UK

Device

Desktop PC, playing through various Sonos speakers

Operating System

Windows 10

My Question or Issue

A few months ago Crossfade was working perfectly for me when switched on through Spotify settings on the desktop PC, but now it no longer works at all.  I also use Spotify using my iPad and iPhone 8, but the "playback" settings are "not available when listening on another device", so I can't set up crossfade using either of these devices.  Crossfade is also switched on for Sonos. Very frustrating - any suggestions appreciated.