There's a few reasons you may be having issues uploading your video. Usually, it's just the size of the file being too big.
Videos that are filmed on smartphones can become quite large. This means that when uploading to YouTube with a 3G, 4G or WiFi, connection, it can drop out, timing out your upload. This is not an error with your phone or YouTube and it is suggested that you ensure your internet connection is strong prior to uploading.
You need to ensure that you are signed into the YouTube App on your smartphone prior to uploading videos through the camera roll. There can be several issues when uploading directly from your smartphone due to permissions settings on third-party Apps. If experiencing difficulties when uploading through the YouTube App it is highly recommended that you download the video onto a PC and uploading from there.
Once your video has been uploaded to YouTube, it will start processing before it is displayed. This can sometimes take hours. Your computer does not need to stay on this screen for the processing to complete. You can turn off your computer, have a sleep, and check it in the morning.
If you do not have access to a high-speed internet connection, then splitting your video into smaller sections may be a suitable option. You can use the YouTube video editor or download a video editing application (free trial of Camtasia is easy to use) and watch the video below to see how to split your videos before uploading them to YouTube.
Video is over 15 minutes
If your video is over 15 minutes long, to increase your limit, you may need to verify your YouTube account. See here for instructions: https://support.google.com/youtube/answer/71673?hl=en