I’ve had that happen on my forum with a couple of links, but within hours. One link refused to show - other than a pop-up for me to log in or sign up. I don’t use FB myself. The next time I clicked on the link I got the expired URL signature message.
One thing I did notice is that when I scrolled down to the user’s post, the video seemed to appear “normally” for a split second, then was greyed out, Some time later I got an “unsupported video mime” error.
Here’s what shows on the first link the user posted:
When she posted the following link I got the expired URL signature:
https://video-sjc3-1.xx.fbcdn.net/v/t42.9040-2/116666410_322146822242699_3960034854420681283_n.mp4?_nc_cat=100&_nc_sid=985c63&efg=eyJybHIiOjUzMSwicmxhIjo1MTIsInZlbmNvZGVfdGFnIjoic3ZlX3NkIn0%3D&_nc_ohc=9eR3Bm0BQjgAX9JECJk&rl=531&vabr=295&_nc_ht=video-sjc3-1.xx&oh=95b3101a1253ab3f394e413c05b8a5a6&oe=5F2D2AF4
She ended up just posting the YouTube link to the video and that OneBoxed and worked fine. The YT link: