Grouping devices in app does not work

Prerequisites

Volumio Information

Volumio Version: 3.819
Hardware: Raspberry Pi 3b+
DAC: Hifiberry Pro +

Debug Log

Steps to Reproduce

Additional Information

Select speaker icon > group devices. Select ‘add’ a device

App will return, but grouping is not shown. Playback is not commenced on secondary device

Expected behaviour: Seconday device is group and starts playback linked to primary device

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