A custom Lightbox ad must have a format hosted in:
- A) DoubleClick Campaign Manager
- B) AdWords
- C) DoubleClick Studio or AdWords
- D) DoubleClick Studio
Explanation: Custom Lightbox ads must be hosted in Doubleclick Studio, trafficked from Doubleclick Campaign Manager (DCM), and implemented in AdWords.
Read more here: https://support.google.com/adwordspolicy/answer/6135143?hl=en