We ran out of propane last night, got more today, and now we can't get the pilot to light... please help!

Which pilot light on what?

You apparently now have air in the line between the tank and the furnace. You must now hold down the button for lighting the pilot light until the gas in the tank pushes all of the air out of the line and the gas reaches the furnace. That can take quite some time because the orifice for the pilot light is quite small.

It is either that or open the line and purge it of the air.

Recommend holding the button down.

Yes, I had to light the heater in my new business location last month, it had the gas turned off before, I was almost 15 minutes bleeding the air out of the line trying to light it

Hold in button to light it until all air is out of the pipe then light it. When you run out of gas air gets in line and it takes a while for air to get out of line. It will take a while to light it, but all will be well if you keep holding in red button or knob until the air is out of line.