Power not being applied to the glowplugs. You really need to put a meter on the output large lug on the relay and watch the voltage while turning the key on in the morning. It your controller card is working properly you'll immediately have ~12-14v there until the wait light goes out and it will continue for another 10 or 15 seconds after you start the engine. Of Course these times are dependent on how cold it is out.
If you don't have power there the next step is to bust out the manual and follow the instructions for trouble shooting the Glow plug system. Essentially the Glowplug controller card applies a ground to one of the small lugs on the relay, The one with the blue wire. So You'll be looking to see if that is working properly. If you determine that your card has failed, the repair is very easy if you are good with a soldering iron and cheap (less than $10), or you can always convert a manual system.
Hope this helps!