Not familiar with the JVC 4K Smart range and maybe post the full model number of the television to see if anybody who owns this particular television can confirm they have downloaded the NOW App from the television Apps Store.
Would have thought if there is no indication of the NOW App or doing a search of your television Apps Store, then maybe the NOW App doesn't support your JVC television.
When doing the search from the television Apps Store, make sure if using a VPN is set to the UK or switched off and the television is setup to the UK (assuming you are based in the UK).
Also maybe go into your television menu settings and check the firmware / software is up to date.
Here's a current link on what devices are supported, where JVC 4K (2019 models) are on the list but it doesn't specify any full model numbers.
Because i am not familiar with JVC 4K televisions by going on the list if JVC offered 4K 2020 & 2021 models then i am not sure they are currently supported.