Scit
Although it's rare, some video-ads have additional conditions before they pay out.
If I'm guessing right about which video you're referring to (I just found it), it has a red 'like and share on Youtube' button just under it. I don't know if you have already tried doing that, but that may be part of how to receive your GCash.
I just tried it, no go. Usually the ones that require Youtube subscriptions or Facebook shares will whitescreen about five seconds in to request it (and they have a bad habit of not paying out, too!). There are quite a few other videos with the "like and comment on Youtube" or "share on Facebook" button that don't require it to pay out. I'm not sure what's causing this one to not pay out, but it's just weird.