Some possible reasons resulting in low RF signals and shorten the distance of transmission leading to the invisibility of Helium Hotspots include:
Obstacles, including buildings, mountains, and forestry in a comparatively dense environment;
Possible Electromagnetic Interference, Line of Sight Interference, Fresnel Zone Interference, or RF Interference existing around cities;
Weather Conditions;
System Operating Margin, Shadowing, and or Link Badger.
Please refer to where should COTX X3 be installed?