All possible reasons the error can be thrown.
|A size in the ad unit is too large or too small.
|A size is an aspect ratio, but the ad unit is not a mobile ad unit.
|A size is video, but the video feature is not enabled.
|A size is video in a mobile ad unit, but the mobile video feature is not enabled.
|A size that has companions must have an environment of VIDEO_PLAYER.
|A size that is a companion must have an environment of BROWSER.
|Duplicate video master sizes are not allowed.
|A size is an aspect ratio, but aspect ratio sizes are not enabled.
|A video size has companions, but companions are not allowed for the network
|The value returned if the actual value is not exposed by the requested API version.