Any time a stand up post isn't working, the first thing I do is check the wires to see if they are connected and the leafs on the other end to see if they are making contact and clean.
When you press the switch with your finger, you should see metal making contact somewhere. Check that contact. As LTG stated, if that's dirty it'll need to be cleaned. If that's not making a connection at all, it'll need to be bent back into place.
If it is making connection and the wires are all securely fastened, then you have bigger problems. But 99% of the time, it's something simple.
