Your finger needs to be touching the black strip on the lever. Don’t tap the lever too gently. Make sure you pull the lever all the way down. Hold it in place for a second to ensure that it registers.

If you have an iPhone 5 or 5c, make sure you are using the adapter.

If none of those solutions work, launch a VR experience then remove your smartphone and tap the gear icon at the bottom of the screen. Follow the prompts to configure your viewer (you may be required to download the Google Cardboard app). Follow the prompts to scan the QR code inside your viewer or use the QR code below.