I had this issue. What it turned out to be for me was that when I left my computer (laptop) unattended during the night, it went into an automatic 'sleep mode' after a while, which paused all my downloads, stopped all my running processes. I see you say this has worked for uploads to youtube, but do you mean uploading a video which has already been exported or uploading a video directly form VideoPad to youtube? If the video has already been exported, then it's possible the upload time to youtube is less than the export time for a video, and it finished the upload before it goes into 'sleep mode'. Is it possible that this could be your issue?