Try using a mouse and click on the country code to change it or perhaps it'll automatically change when you enter the number try it.
Suspect it may be related to the origin of your Google account, iv had similar issues with our Sony bravia which has Google TV. My Google account was created when I lived in the UK and therefore the Google store was set the same and had UK app purchases related to it, my gf's account was setup in Aus. If I only login my account, I cannot download some Australian based TV apps. If I login with my other halfs, I can. If we have both accounts signed in, it seems to prioritise the first login. Googlemake it almost impossible to convert your account to a new region because it will also have a google wallet and other services associated with it. Quickest and easiest would be to create a new account to be used with your TV, sign out the others and sign in with the new aus account. If there are any paid apps you want from your old account that are not region specific, sign in with that account first, download them, then sign out and switch to the new. Hope this helps
Just a question were you able to resolved the issue cause I am experiencing the same problem
Is this Disney Hotstar from India?