There are many factors may cause loss of communication when doing Autel J2534 programming.

Here are some pointers specific to Autel and Java:

Connections:

Connect the J-box to the PC. An icon should appear in the PC’s system tray.
Connect the J-box to the vehicle.
Open the GM / AC Delco software.

Java:

Verify you are using the same version of Java as required by GM / AC Delco.
If the Java version on your PC is newer than the one required by GM / AC Delco, you will have to ‘rollback’ to the version required.
If the Java version on your PC is older than the one required by GM / AC Delco, you will have to update to the version required.
After making these changes you may want to change Java’s default settings to DISABLE automatic updates.

Although not frequent, updates for the VCI and the J-box are released and should be installed.

Turn on Autel.
Click icon for VCI MANAGER.
Click the Update button.