I tried to upload my video, but this error show up everytime I try to upload, Snap is uploaded successfully but when I click Submit, they show "Unknow Error".
This might be server-side error, or this is because of Dtube/SteemIt's policy limit user to post every 5 minutes, but if it is the later, they should display a more informative dialog like "Upload Error - Upload limit [ You may only post once every 5 minutes.]"
I figure out that if I wait for a few minutes, and Submit again then it will work!
Hope this is helpful! So far I love DTube and Steemit's community and hope I can contribute more.