How old is your TV set? JVC changed their operating system around 2016 and it might well be that certain apps aren't compatible with older models. (App compatibility problems are common with people trying to download them to their TVs and definitely the most obvious reason for an app not showing up in a TV's app store).
To check whether my assumption is correct, use the contact form here
https://uk.jvc.com/support/contact/
ensuring that you include the
exact model number (from the back of the set) in your message to JVC.
You might need to access Disney+ through a separate device though, such as a Roku one (with prices from £24.99 to £49.99, depending upon the model you select)
https://www.roku.com/en-gb/products/players
or an Amazon Fire TV stick (with prices from £29.99 to £49.99)
https://www.amazon.co.uk/Fire-TV/b?ie=UTF8&node=5157838031