Diagnosis
Physical obstruction or moisture ingress. Debris behind the button or corrosion on the internal contacts is preventing a reliable electrical connection.
How to Fix It
Power down the device by removing one battery. Use a can of compressed air to blow around the edges of the button. Press the button repeatedly while the battery is out to help dislodge any particles. Reinstall the battery and test.
If That Didn't Work
The internal button switch may be failing. This requires disassembly not recommended for users. Contact Blink Support. If under warranty, they will likely replace the unit.
Heads Up
The Blink Video Doorbell is weather-resistant but not waterproof. A direct, high-pressure stream of water from a hose or during intense sideways rain can force moisture inside. Ensure it is installed under some form of eave or cover.