The latest version is 4.9.7.798 for V2 cameras, and you need the latest App on your device for Android that is 2.23.21 and for iOS the latest version is 2.23.23
I have 7 V2’s and they are all working with the above firmware.
You may want to read this post also if you are using a device that is below Android 7 or iOS12
Important message for people using device operating systems (OS) lower than Android 7.0 and iOS 12.0