Here are the most likely causes:
Data plan - Confirm that your plan is active (green) in your command center
Batteries - Try replacing your AA batteries with fresh, high-quality batteries from the same pack (Energizer Ultimate Lithium are best)
Connectivity Reset - Turn your data plan to Canceled for between four and five minutes, then turn it back to your desired plan. Sometimes reinitiating a cellular connection can jump start your camera. This is an easy one to do remotely, possibly saving you a trip to your camera.
Settings - If your camera is connected to a weak 4G network, it might not be able to send medium-resolution pictures or video. Try resetting your camera settings to factory defaults from your command center app (Cameras page > click camera name > "Restore Factory Default Settings." Then request an image with the Quick Pic button. After doing this, set a timelapse for 6-hours. This will trigger a picture every six hours and help us troubleshoot further. These settings updates and quick pic should take effect overnight.
SD Card - Occasionally SD cards must be reformatted. You'll need to visit the camera for this. Slide the camera to SETUP mode, press the Up arrow, then the MENU button. Then navigate so that format is red, press OK, then confirm. After this is complete, press the up arrow.
Contact us for help! We know how frustrating this can be, you can always contact our support team and we can help!