I have a development skill "The great courses plus" in my account.
2-3 weeks before it was working fine.
But Now when I say Alexa Open "The Great Courses Plus" it respond
"I couldn't find any enabled video skills. Go to the music, TV and books section of the Alexa app and enable the video provider you want, and then link your account and complete setup"
The great courses plus is a custom skill which uses AUDIO_PLAYER