The trunk on my 2000 volvo s-40 wont open

You'll need to insert your key into the trunk lock. prior to doing this you'll need to use the automatic lock on the driver side of the vehicle, hit the unluck button twice. Torn the key in the trunk to the left, you may have to slightly press the trunk button in while doing this and give it a lttle wiggle after the key has been turneed to the left push the button all the way in, if this does not work repeat the process but reverse to the right instead of the left.

This manually disables the remote lock for your trunk.