Are you experiencing issues with your upload? We recommend to try these solutions:

a. Make sure your video plays correctly and it is in the right format
Play your video on your device in a common media player and make sure that it doesn't freeze. Please make sure your video file is in the correct format: 

Supported container formats and codecs:
MP4 (H.26x, MPEG-2, MPEG-4), 3GP (H.26x, MPEG-4), AVI (Divx, XviD etc), WMV, MOV/QT (MPEG-2, MPEG-4), MKV, WEBM (H.26x, MPEG-2, MPEG-4, DivX, XviD, VP6), FLV (VP6, H.264, MPEG-4).
Supported audio codecs:
AAC, MP3, ALS and AC-3.

b. Change your file name
Try to upload your video file again and please make sure to change the name of your video file before you do so.

c. Compress your video
Use a programme like the free tool "Handbrake" to compress your video file. Click on this link to download the software and learn how to use it here.