The problem is I can't tell from this information where the problem is. Your report that "POS 3 is successfully connected to the server but it's product updates are not showing" is contradictory. All the data files are stored on the server and the all the computers should be accessing the same files. If the product file is updated then every computer connected to that file should show the same thing. That would indicate that POS 3 is not connected to the server. On POS 2 & 3 open the Help window and look at the Database path at the bottom. They should be pointing to the same location on the server.
BTW - if you are in a hurry, email support for faster response than the forum.