You're PACS settings can be found within your Configure settings under the tab "DICOM Device". You can Add, Edit, or Delete your PACS connections here.
This problem is caused by your Nautilus PC not being able to see your PACS server on your network.
Check that your are connected to the same network as your PACS.
Confirm you have to correct IP Address and Port settings.
This problem occurs by your Nautilus PC not being able to communicate back and forth between your PACS.
This is usually a PACS side configuration issue by not allowing communication from the Nautilus PC. For an echo to be successful, the PACS server must be setup for both the static IP and AE-Title of the Nautilus PC to be allowed a connection.
It is also possible that it is a firewall or antivirus issue. Try disabling your firewall and antivirus settings to see if this is blocking your connection.