The crutch is a fork where the pendulum rod sits in. You'll notice the pendulum is not directly connected to the clock gearing or wheel train. The fork transfers power to the pendulum and gives it the push. There should be a small gap between fork tines and the pendulum rod so the pendulum has freedom. The crutch goes up to the top and is fixed to the "escape arbor" which is then interacting with the wheel train. The pendulum is connected to a "suspension block" at the top by a thin flat spring. If this spring is broken the clock wont run. Check this too. They usually have two leaves with a gap between and joined by two pieces of brass top and bottom. The spring passes between a brass slit that can be adjusted with a small key above 12O'clock on the front. Another tip, if you take the pendulum off when the clock is level and in beat the crutch will tick rapidly if the clock is wound. I will often test a clock for "she's a runner" this way, you can lift the clock left and right to see which way it needs to go. If this happens then the clock would only need a clean and oil.
Now the beat adjustment screw is a luxury and not all mass produced clocks have them. It's recommended to let an experienced clock repairer adjust the beat the following way as they will often simply bend the crutch rod to get it in beat. Check to see if your clock has leveling feet , many do.
See picture, I've lifted a pic off the net and annotated it. Now this is a "count wheel strike" your's might be a rack strike and will look different at the back but similar. You'll see the crutch, the pendulum must be in the fork slot (pendulum missing in the picture). This clock would be set in beat at the factory by adjusting the pallets on the arbor when out of the clock (or by clock repairer). They are friction fit and move with a bit of force . They are connected to the crutch or basically the crutch is mounted on the back of the pallet arbor which does the ticking.
So check your pendulum suspension spring is not broken.
Check the pendulum is actually hooked onto the bottom of the spring
Check the pendulum is in the crutch fork slot
Ensure the pendulum is not fouling anything
check the clock is wound
give the pendulum a slight push. Listen to the beat - tick , tock , tick , tock not tick tick , tick tick like it's galloping. Failing that Mathew would sort it out.
Any of those problems will stop the clock. It sounds like your shelf is level, they are heavy clocks.
I've repaired many of those types. The two most interesting a black slate clock imported into Aus after WWII by the owner , the last service was scratched into the rear plate with date 1942 and clockmakers initials with a swastika gouged next to it, it almost needed two people to lift it and yes very painful to keep moving around when servicing. The other a very large porcelain gilt egg with a missing pendulum . I could barely get my hand inside to work on it. The correct length pendulum would not fit inside , too long, what a mystery. I figure it was a compound pendulum meaning a small bob at the top , counterpoised with the bottom. The other theory was that the movement was not original to the clock and I've not had two clocks with the same length pendulum but the compound pendulum worked.