Make sure the fork is engaged with the small pin on the balance wheel. You may be able to see if power is getting to the escape wheel by gently rocking the balance wheel back and forth and see if the escape wheel is released, one tooth at a time. In turn, the balance wheel depends on the escape wheel to give it a little kick (via the fork) to keep it oscillating. They are joined by a fork and the escape wheel depends on the oscillation of the balance wheel to catch and release it (via the fork) so that it doesn’t spin away like a mad thing. The escape wheel and the balance wheel are in a kind of symbiotic relationship. The mainspring is constantly putting pressure on it, trying to spin it.

The escape wheel is the small wheel with sort of squared off teeth. If you decide to pull the movement apart out of curiosity, you will need to release the pressure in the mainspring so come back here if you decide to do that. (doable without disassembling the movement but a delicate operation).

Rob the balance wheel and spring from an identical clock. Has it fallen out or is it just not showing up in the photo? It should pass through the slot indicated and the outer end should be trapped in another slot or hole. I can’t see the broken balance wheel (spiral) spring in your photo. The white wheel moves constantly but too slowly to observe however, in your clock, it can’t move because the balance / escape wheel mechanism can’t do its catch and release thing, so it remains caught. The white wheel drives the time function (extremely slowly) through a train of gears that is caught and released by the balance and escape wheel mechanisms…that’s the tick tick tick sound you would normally hear. The grey wheel drives the alarm mechanism when the alarm is released. There is only one mainspring that powers both the alarm and time functions. I pulled the movement out of one and the setup is very similar to your clock. They have been in my family for years, but I’ve never had to work on them. I have two Westclox “Big Ben” alarm clocks made in Scotland, but they are all metal – no plastic. I doubt there is a problem inside the mainspring barrel (“pill-box”)

Download old ben clock