DIAGNOSIS: A solid red LED means the camera is in setup mode, but it's stuck there. This usually happens after a failed setup attempt or a factory reset.
FIX: You need to force a hard reset and start setup over. 1) Unplug the camera. 2) Hold down the physical reset button on the bottom of the camera with a paperclip. 3) While holding the button, plug the camera back in. 4) Keep holding the reset button for about 10-15 seconds until the red light turns off and then comes back on solid. Then let go. 5) Now, in the Blink app, delete the old camera from your system (if it's listed) and add a new device, following the prompts.
IF THAT DIDN'T WORK: If the red light persists after the hard reset, try using a different USB power adapter and cable. A weak or faulty power supply can cause boot-up issues. Use the one that came with the camera if possible.
HEADS UP: During setup, make sure your phone's Bluetooth is on and you're very close to the camera. The initial handshake uses Bluetooth. Also, ensure you're connecting it to a 2.4GHz Wi-Fi network, not a 5GHz one.