First, you'll need to go to Devices - Mixer (or press F3). At the far left, there is a Reset Mixer button which looks like ()<< you need to press. When asked, press Reset All.

Then, go to Devices - VST Connections (or press F4). Click on the Outputs tab, open up Stereo Out to where you see Left and Right. Beside Left under ASIO Device Port choose 1 Analog 1-2 and beside Right choose 2 Analog 1-2.

You may want to re-save this project so you do not have to re-configure it next time you open the project.