Have you tried swapping the boxes around to see if the problem follows the box?
Can you also check using your remote Home > Help & Settings > Settings > Network.
At the left hand side of the screen it should show last status which should hopefully say connected. If it doesn't, or it hasn't made any further connection attempts since you last had the problem then click on Connect to Virgin Media Service now.
You can also test your network connection from the same screen, ignore the port configration test section.
You can also run a speed test which will show if you have any network issues affecting the strength/speed.
To run the speed test with your remote.
Home > Help & Settings > Help > Our Other Products > Broadband > Take a Speed Test > Press Play (DO NOT PRESS OK)
There may also be an issue with HDMI leads, they ened to be HDMI2.2 compatable to run Netflix/Prime - this link may help error-codes/604 (ignore the error description)
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali
It's really strange - on the first Tivo box I can get in to Netflix and Amazon Prime, get through to the screen which shows all the episodes, when I click on the show it says ""We're having trouble playing this title at the moment. Please try again later or select a different title" on Netflix and "Something went wrong" on Amazon.
When I choose the same shows on the second Tivo box it works fine.