Cockpit - A Compatible Version of Cockpit is Not Installed on X

Greetings,

Some time ago, I setup a Cockpit server and joined several servers and workstations to it, and this configuration was working pretty much flawlessly. Some of the workstations and servers had updates issued to them, and since then the Cockpit server has been unable to reconnect to those machines, and it's truly not obvious why. Now, of course you could rightly tell me to reconcile updates betwixt these machines and therein lies the culprit, but I'm not convinced it's that simple.

As stated, Cockpit still has visibility to some of the computers it originally managed. In fact, some of these received the updates and are still visible to it. We transact SSH over a custom port, but these provisions have been made in firewalld to all participating computers. Furthermore, from a terminal on the Cockpit server, I'm able to manually SSH into the computers that are supposedly inaccessible without exception. The version of Cockpit that runs on both the server and the clients is harmonized on 176-4; this is verifiable by both yum and rpm. Yet every connection attempt was met with the error that comprises the title message. This was clearly bogus and perhaps misleading.

We do use a Cockpit-specific service account that is passed between all participating computers. This account has sufficient privileges to execute both Cockpit and its constituent plugins on each guest. In a fit of desperation, I removed the user from one of the guests, removed the guest from the Cockpit server, and re-added it with the option to synchronize the service account back to the guest. Lo and behold, everything is kosher once again. While I'm prepared to run through all of the guests and do this - there are less than twenty of them - I'm concerned that something may be interfering with the stability of Cockpit such that if another update is issued (perhaps this isn't even the culprit, however, it's chronologically the only aspect I have to work with), it will break the connectivity and I'll have to repeat this process all over again. I have a similar problem with GNOME provisioning through GSchema, but this is a bit more obvious and the fix is consequently clearer.

Can anyone shed some light on what might be happening here? I'll provide any additional information that I can. Thanks!