Your server is obviously not connecting the the till!
Do you have 2 licences & have you specified the correct pc name / IP address for the 2nd pc?
If so, your 4POS Domain controller should show 2 pc's & both active & connected.
An easy way would be to see if you can access that pc over the network from the main pc. Eg. \\till2\c\4pos
Also check that you can create a file on that pc from the main. Right-click - new text.
If not - fix your network settings!