Sorry!
You have come to the wrong forum for this. Many here won't even know what a Horizon Box is.
This is a forum for Virgin Media UK customers, & our TV boxes are TiVO's, which are totally different.
If you have been speaking to the online chat linked to this website, you will also be talking to VM UK staff, who won't be able to help you. VM UK & VM Ireland are totally seperate companies.
These are the contact details you need:
https://www.virginmedia.ie/contact/
Good luck