I have a device that does this. It is a Zooz power strip that has child devices. Does your device have child devices?
It sounds like I am seeing the same thing. In my case it is on a C5 in my shop. I have the device shared and on my C7 hub that contains my rules I can see it as a device that is shared. When I click the + sign it ask if I want to share the device, I click yes but nothing happens. The device still shows as an available shared device but it is not added to my C7 for use. I asked about this in another thread about the Zooz power strip back in April and got no response. I ended up just moving the rules to my shop hub, so as not to have to share it, as the shop hub is basically a stand alone hub with rules. I had forgotten about it until I read this post. So this was a few revisions back on firmware, I am currently on .147
