First off, if yo plan to re use the belt, don't open it up to have a look see. That usually results in tiny parts jumping out. I can't see the entire belt mechanism but most rely on a dangling fob which caused the belt to wind up when fob moves forward (as in a crash). When the fob settles again, the latching mechanism releases and you can extend the belt. Each belt is designed to be installed in a specific orientation and will lock up if it is even just a bit away from that orientation. Belt in hand as you have it, gently tug and release the tongue while you slowly reorient the entire belt mechanism. After a few tries you can usually find the sweet spot and the belt will release. I find that keeping my own tongue pressed in my left cheek often speeds the process.