Hab da mal einen Beitrag von @cryptosergio in einem anderen Topic gefunden, vielleicht hilfts:

„The Snap image must be uploaded while the video is uploading.
The video must be below 1Gb.
You need to wait until the video has been uploaded to submit (it can take quite long depending on the network)
Some times, even following that it doesn't work, probably because the network is saturated. If that's the case go do some nice fun stuff for some hours and try again later :)“