Argon2 streamer locked invisible by another family member

[jetpacker-tomas]

We have two Argon2 Spotify connect streamers . All family members have Spotify premium accounts. When one of my kids have been playing through one of these devices and "forget" to disconnect , that streamer becomes invisible in my Spotify app.  The "invisibility" occurs both on my windows laptop and my Android Phone.
 Is there a way to disconnect "him" from that device ?

I tried removing power from the device for say 30 seconds, - did not help