Yup we made a big boo-boo. Somehow we ordered the 24v coil ones and not the 12v ones. We have to order new relays now and will send everyone that is effected new relays as soon as possible.
If you have a volt meter you can make some more tests. Connect the volt meter across the relay coil. That should tell you if you are getting sufficient voltage to drive the coil. If you have an o-scope that is better. You may be getting something other than pure DC to the coil, and an o-scope will show what kind of waveform is present. You said the realy was buzzing. Never should happen with DC.