I want to add to ensure you render your video using the h.264 codec.
I also had this issue uploading videos to Stripchat, but in my case I originally rendered the videos using something like h.264qse or h.265, whatever the default in OpenShot was. Re-rendering the video using h.264 allowed the video to go through.
@Charlie_SC I would recommend adding a list of supported codecs to the
technical requirements info page.