Did it work fine after installation and has now stopped ?
If it did, can you check for any “known network faults in your location - Look in 2 places
1) Try the “check service,”Area status webpage (https://www.virginmedia.com/help/service-status)
2) Then also Try the “free & automated” Service Status number - 0800 561 0061 - which usually gives the most up to date info. and tells you of more local issues and fix estimates, down to street cab/ postcode level.
If it didnt - Call the Pre-installation and delivery team on 0800 052 1734 and book another Tech install to sort it out - open 8:00am to 9:00pm Monday to Friday, and 8:00am to 6:00pm Saturday and Sunday