I'll take that.
What happens is that TV's are for general consumption so in order to prevent shenanigans and heartache / confusion, they limit add-ons to trusted developers / companies.
In dev mode you can install whatever you like, I'm guessing to cover devs who're obviously testing what they're coding as-they-go.
I've forgotten the procedure on Google TV's (like the one
@MadAsAHatter is talking about), but it's just a matter of hitting enter / yes over the appropriate sub-menu title.
@MadAsAHatter, Check that your TV hasn't run out of disk space, bro; that's most often the reason people can't install anything new. If you're having trouble with FuboTV customer service, you can also check
https://fubotv.pissedconsumer.com/customer-service.html for support information, and of course, please try Dev Mode.