Firstly, you'll need to check that your Oculus is properly connected to all the laptop ports.

*Note: is you are using an Oculus Rift S you will need to make sure your headset is fully connected to the HDMI and USB ports on your laptop. If you are using an Oculus Rift device, you will need to make sure your headset and sensor(s) are fully connected to the USB and HDMI ports. 

If you are using a Dell Alienware laptop, you may have plugged your Oculus into the Ethernet port on the left hand side of your laptop. You'll need to plug this into the USB port (between the Ethernet and Headphone ports) instead. *

If your Oculus is still not launching, you'll need to check that you've enabled downloads from Unknown Sources. 

Open Oculus and go to Settings in the left hand side bar.

Once you're in Settings, select "General" on the top menu

Make sure that the toggle next to "Unknown Sources" is set to "on". The toggle will appear blue when this feature is enabled.

Return to the Web App. You should now be able to launch and view a scenario.

Enjoy!