I have tried the add-on with both Blender 2.90 and 2.91. Basically, it does not find or connect the computers. I have 2: one with Windows 10 and one with the latest Ubuntu with fixed IPs in a LAN network. I have had no problems with the add-ons' installation and activation. Basically:
1 - If I create the nodes and provide the right name, the software finds out the right IPs; but nothing else happens. No signs appear to enable or disable the nodes.
2. If I try to sign in to the cloud account, it does nothing. I do not know what happens with the account. To get into this forum, I had to do "sign up" instead of "sign in", although I already had an account but the system did not recognise it (is the cloud account also another different account? Or do you have to have money in it already?).
See in the picture how the new node displays and the feedback below after clicking the gears . Nothing else happens. No error message, no more icons on the left of the "i" icon in the node. This is trying from Windows, If I try fron Ubuntu, the same happens.
Note: the curious text of the "connect" button has to do with a quirk of the Catalan version. I put Blender back into English to try again and it displays "connect" correctly; but the problem remains.