Your users report that when they restart their computer with Xinet Pilot installed, they are seeing the blue error "To use Xinet Pilot, type the URL to your Xinet server in the preferences sheet above" alert. You have already configured the Xinet Server URL within preferences.
Within the server access_log, you see a blank GET request when the blue screen appears. Quitting and restarting Pilot temporarily resolves the issue.
The user has configured Xinet Pilot to start automatically with their computer. Xinet Pilot attempts to connect to the Xinet Server before the network adapter is ready. After the initial failure, resetting the URL or restarting Xinet Pilot allows a new connection.
To solve this trouble, Remove Xinet Pilot from the default Startup Apps on the user's computer.
See Open items automatically when you log in on Mac for assistance configuring the Default startup apps on your Mac.
See Add an app to run automatically at startup in Windows 10 for assistance configuring the Default startup apps on your Windows PC.