CTV app is definitely a convenient way to keep up with the shows on the go. When was the last time the feature worked for you? Have you made any account changes recently?
I just tried the On Air feature via the app on my iPhone and I was able to access the content without any issues. What device are you using? Can you please try to clear the app cache and log back in to see if it lets you watch Live TV via the app?
Thanks for the additional info; it's good to know you can log in to MyRogers on Amazon Fire TV Stick. Can you access CTV on other devices running iOS or Android? Also, can you log in to ctv.ca and access the channels you're subscribed to?
The issue you're experiencing could be related to CTV GO App's requirements. Even though Fire OS is built on Andriod, it may not be supported by CTV GO App.