A custom Lightbox ad must have a format hosted in:
- DoubleClick Campaign Manager
- DoubleClick Studio or AdWords
- DoubleClick Studio
A custom Lightbox ad must have a format hosted in
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