Resetting is completely different from factory reset.
Factory reset is putting the box back to factory settings in another words erasing everything on it and as if your starting it from scratch.
As a suggestion you could try unplugging your router for a few minutes?
It might be worthwhile speaking to Now TV staff via live chat.
Just make sure to click “chat online” within the green box.
Although with the app being third party staff might tell you to speak to the service directly.
I am 100% convinced that roku/nowtv United Kingdom has not received the latest update from mlbtv as this same thing happened last year. The person asking you to do factory resets on your nowtv box is just speaking absolute nonsense. Last year someone had to email mlbtv and roku to get this sorted this side of the pond. I subscribe to mlbtv and at the moment the app on nowtv doesn’t work. Someone at nowtv needs to ask the good people of mlbtv to send over the update so we can watch it on our tellys.