"I blew compressed air, but it just knocked some insect debris down in the line, nothing came out other side."

That would indicate it is blocked.

You can either install a new line, or try getting some methanol into the line to thaw it out, then blow it clean.

70-80% methanol and water actually has a lower freezing point than pure methanol.

Denatured alcohol can also work if the ground temperature is not to low.

Thanks. Maybe i will try that this weekend. its been so cold i havent been motivated to work on it - tonight is supposed to get -3 F, but warming up on the weekend.

Pour the methanol in now and let it work on thawing the line until the weekend. Then pour some more in. Pour it in from both ends.

You could flush the line with methanol, then blow the methanol out with high pressure air and finally seal the line on one end and attach a vacuum pump on the other, then pull a deep vacuum to dehydrate the line,,

But lets be real here:

The line is only 12 feet long and we don't have clue as to what type of debris may be in that line, or for that matter, the age & physical condition of the existing line.

You could install a new line for a mere fraction of what the labor cost would be to do all that messing around.

If the ground is frozen rig it as a temporary line and as soon as the ground thaws you could bury it.