The people who provide the forum platform have identified a bug around video uploads that several folks have had problems with. The problem is triggered when the same video is uploaded more than once. The multiple uploads might be from a single user or from multiple users. They are working on fixing the bug.
Meanwhile, here are some workarounds for avoiding this bug:
Use Youtube. This works for me.
If your video won't upload, use video editing software to edit it slightly.
Select the video using the From My Videos in the Insert Video UI
Below is the message from our support people with details about this bug:
This has been discovered to be a bug which occurs when the same video is uploaded multiple times in the community. If a user uploads a video, then uploads the same video again, it results in the second attempt being marked as a duplicate within the video processing engine permanently. When this happens, the community UI does not show the video anywhere because duplicate status is considered an error state (moderation pages, video gallery page, etc.).
However, a problem arises if the user tried to upload the second attempt from a post. In that scenario, the video will appear in the post, but instead of the actual content, it shows "Content Unavailable - Unknown Content Specified". This can happen if two different users happen to have the same video on their computer as well.
If any videos are in this state, they are still attached to the user that uploaded them, but they don't show up in the user's gallery page. However, if the user goes to create a post and selects "From My Videos" on the pop-up dialog after clicking the video icon to select a video they have already uploaded, they will see the videos that are in this error state and they can choose to add them to their post.
Retired Community Manager for Solid Edge. This account is no longer active.