Android: If you are having trouble uploading a video on the Android app please make sure it's a support video format. Seesaw supports .MP4 videos using video codec x264 and audio codecs mp3 or aac on Android.
iOS: For best results, upload videos using the iOS app. You can upload videos saved to the camera roll by tapping the "Camera Roll" button in Seesaw or by using the Open in / Share Extension features in other video apps.
Website: Make sure you are using the latest versions of Chrome or Firefox. Keep in mind, if your file is large, it will take while to upload and process your video.