AVG Internet Security Not Updating

Hi, I do local computer repair and was called out to a customer where their AVG Internet Security had stopped updating. The system has been installed and updating since June 2017 without issue. After checking the system I uninstalled AVG then ran the AVG removal & clean processes and downloaded the latest version of AVG Internet Security. After several attempts this wouldn't install failing with an unknown error after a few minutes. Eventually I removed the computer and connected it to my own broadband connection and the installation completed and updated without issue. AVG was then activated with the customers license key.

I returned the computer to the customer only to find it wouldn't updated again with the error:

Unknown Error
Total Time: 5:42
Download Time: 5:01
Downloaded Files: 20(0.00 KB)
Server: Download g3903904 Update Server
http://g3903904.avinitro.u.avcdn.net/avinitro

Program

Current Version: 18.2.3046 (build 18.2.3827.0)
Release Date: 01/03/2018 11:53:30

Removing and cleaning AVG at the customers location has the same effect as before in that the program will not install but connecting it to a different network allows it to be downloaded / installed & updated without issue.

Everything is pointing to the customers broadband connection but everything else on the PC is working without issue. New HP desktop running the latest updates for Windows 10.

Thanks for any help.

Tom