MediaTailor Channel Ad Playback Fails - Ad Tags Work in MT Configuration Tests

Platforms: AWS MediaTailor / S3 Bucket / MediaConvert

Overview: Ads fail to play in channel assembly funneled through tested ad server configuration.

Detail: I have two tested ad server configurations (one generic provided by Google for testing and the other in-house) using HLS encodes created in MediaConvert using VOD playback from a public S3 bucket. When VOD is sourced from the S3 bucket as a plain m3u8 file, the ads play perfectly every time from our ad server.

I created a channel in MediaTailor using the same tested content (two music videos), added them to the channel and added ad insertion instructions as follows at 0 seconds so they would be pre-roll. See attached graphic:

I took the channel output URL (less the m3u8 file at the end) and used that as my video content source to create my ad insertion URL and then appended the channel m3u8 filename at the end of this string. In testing this string, the two videos play back to back perfectly and as expected - but no ads. The channel schedule, however, displays strange behavior - before being started, there are scheduled ad breaks indicated after every program entry. After being started these scheduled ad breaks do not display in the first 3 entries (and no ads on playback). See attached graphic:

Any assistance or insight greatly appreciated.

Thanks!!