Hey there, it shouldn’t be required to switch to the Beta release.
My assumption is that the initial pairing with our Pantacor update servers failed. Without this information we assume that the device is not a retail Mark II, and is more likely a Sandbox or other image that don’t use this public key field.
Any reboot it should re-attempt the connection with the update servers, so when you switched to Beta that would also have triggered a new attempt.
So you can switch back to Stable if you want and that will retain the public SSH key field.