HTML5 ad won't play, just a gray box.....

Hello Smarter People than I!

Not sure if this is an issue Im encountering via Animate, but I'll give it a shot here.

Ive built, and published for output, a set of HTML5 ads for a client via Animate. When they upload them to the vendor they use to distribute, all they get is a gray box. Typically my html, when clicked, would start playing my ad. This time, its just a gray box for all my different ad sizes Ive built.

They use a specific DSP vedor to deliver the ads, which have their own specs pretty close to IAB. (images cant be over 100kb, total zipped ad cant be over 250kb, and there's specific code they have me add into the html file, etc). I follow these specs as I supposed to, and since I dont speak HTML, Im just copy/pasting where its supposed to go. This process always works, have done probably 100+ different ad sets and have yet to encounter this. That being said, I'm still a bit of a novice when it comes to this program. I 've got a message in to the vendor, but sure they'll just point it back to me.

Any thoughts? Maybe missed a setting? TIA!