From:
https://www.verizon.com/support/resi...l/voice-remote
"The Fios TV Voice Remote connects with your Fios TV One via a wireless Bluetooth connection so it will still work if your Fios TV One is hidden in a cabinet or other non-metal enclosure—as long as it’s not farther than 25 feet away."
Your remote needs to be 'paired' (linked) with the box. Since it was previously paired to with a different box, the link is now broken and needs to be reset to the new box.