I am unable to get the cardboard icon to display on any 360 videos in youtube. I have Cardboard and Google VR Services installed on my Samsung S5 (just factory reset it, no other apps).
Youtube is updated to 12.15.55. The cardboard app works fine as expected (responds to movements of the phone).
When watching a 360 video the cardboard icon is not available and the video just shows in "flattened" mode. It is running Android 6.0.1 All the other threads I have found on this have been older and deal with updates to YouTube of the OS which I think should not be my issue?
I am having trouble with the same on an S3 too, but thought that might be because it is older.