Hub mesh: available devices not showing up yet some devices are connected

I have four hubs connected with hub mesh. All hubs show in the active hubs on all other hubs.

Hub 2, 3 and 4 show up on all four hubs in the linked/available hubs. Hub 1 does not show in the available hubs section of any hub. But I do have already linked devices from Hub 1 on other hubs. So at some time in the past I was able to select Hub 1 devices to add, but now any new devices I make available on Hub 1 through mesh do not show up on any other hubs.

Thoughts? Thanks.