Can you try with the following steps:
1. Open the scene in formZ
2. Go to Display Options [right-click at the Thea icon in the top toolbar > Thea Render IR Options...]
3. In Distribution settings set Network to Server
4. Start rendering in Thea Darkroom inside formZ
5. On your other machine launch a Thea Client [for Windows open the Start menu and type Thea Client, for Mac go to the Thea Render folder in the Applications directory and launch Thea Client.app]
6. Once the client has been launched select Configure at the left side, and then click the icon in the "Server Address" line.
7. A new pop-up window will appear (Searching for servers...). After a few seconds the first machine will be listed. Select it, click OK and also close the Configure panel.
8. Click Start in the client. After a few seconds the console should inform you that the project has been received. At this point you should also see a new entry in the Network Log about the added client.
Hope this helps!