in pro tools, you need to turn it online. Apple+J or go to Operations menu, then click the online option. Next, (I assume you're trying to Sync with a MIDI cable right, if not, then S/PDIF), you need to turn the MIDI button on in the transport window....if that doesnt do the trick, then click setups, then hardware setups, then there should be a box that tells u what your clock source is...Internal, S/PDIF etc.
If none of that works, then just email Digidesign. tell them what you are trying to sync, which you want to be the Master/Slave, and they should be able to help you out