@Foriusz I suspect the problem is on the Streamable end. It’s a little hard to test with the videos above because some are deleted now (OP plus this post).
In the post with two videos, the second one isn’t deleted upstream, but it doesn’t play for me (note that it doesn’t prompt to download either).
I also uploaded a test video to streamable just now, let’s see how it fares:
Update: it plays correctly for me on macOS/iOS.