Duo-therm heat pump model # 630035-331 Unit compressor comes on but fan does not

Can you give us some more helpful information-- so we can help diagnose the problem:
Like-- what is the outside temperature?--

Have you been able to get heat out of your heat pump before, at this low of an outside temperature?

And which fan are you talking about-- the inside fan, or the outside fan?

Is the inside coil getting nice and warm-- or just barely warm?
and is there frost on the outside coil-- Can you defrost it, but shutting the unit off until the ice is cleared?

Let us know, and we'll better be able to help you to the next step.

Mack B