Signal strength can differ depending on the location and the cellular tower your camera is connecting to. 
It is important to test the signal for your camera in the area you intend to use because it could differ from what you have seen while testing it at home. 
Note that, it is possible for the cell signal of your phone to differ from the cell signal of your camera.

Here are some pointers to maximize signal strength:

• When installing your camera, it is important to screw your antenna tightly. 
• Try positioning your antenna at different angles to check for signal 
• You may power your camera OFF and power it back ON (*only power OFF the camera when all lights are OFF). 
• Try using an External Long Range Cellular Antenna (#V-ANT01).
  

For more information on improving your connectivity, check this article: How to improve your connectivity