Perform a Basic Inspection
 

• First, ensure that there is no debris or obstructions in the sunroof tracks. Dirt and debris can prevent the sunroof from closing properly.
• Check if any visible damage to the sunroof or track system might be causing the problem.
• Ensure that all electrical connections related to the sunroof are secure and not damaged.

 
Check the Sunroof Fuse
 

• Locate the fuse box. In the 2016 Audi A4, it is typically found under the dashboard or in the engine compartment.
• Refer to your vehicle's manual to locate the specific fuse for the sunroof.
• Inspect the fuse to see if it’s blown out. A blown fuse must be replaced with one of the same amperage.

 
Reset the Sunroof
 

• Switch your ignition to the "On" position, but do not start the engine.
• Press and hold down the sunroof close button.
• Continue holding the button for about 30 seconds until you hear a sound or see the sunroof moving slightly, which indicates a reset.
• Release the button and try to operate the sunroof to see if it will close.

 
Lubricate the Sunroof Tracks
 

• Open the sunroof fully to access the tracks.
• Using a suitable lubricant, such as silicone spray designed for sunroofs, apply it evenly along the tracks.
• Be careful not to apply too much lubricant as excess can attract dirt.
• After lubrication, try operating the sunroof to see if it closes properly.

 
Inspect and Test the Sunroof Motor
 

• If the sunroof still doesn't close, the motor may be faulty. Remove the headliner to access the sunroof motor.
• Check for any loose connections or wiring issues.
• Use a multimeter to test the motor; if it has no power, it might need replacing.

 
Consult a Professional
 

• If none of the above solutions work, it’s advisable to seek help from a professional mechanic or an Audi dealership.
• They can perform a more thorough diagnostic to pinpoint and fix the underlying issue.
• Professional servicing ensures that no additional harm comes to your vehicle’s sunroof system.