@Anonymous User Welcome to the community. You can't watch NOW TV directly on the Sony Smart TVs, only some models of Samsung and LG TVs have NOW TV apps (and watching in-browser isn't supported). Have a look at the following list of supported devices as you might find you already have something that you can use. If not, a NOW TV stick is probably your cheapest option.
http://help.nowtv.com/article/Supported-devices
PS If you are trying to watch on a device connected to your Sony TV and that's the device you're having trouble logging in with then try popping onto live chat, they should be able to help. You can get to live chat from the Contact Us page
https://help.nowtv.com/get-in-touch
(expand the Anything Else section at the bottom for options)
