Some NetSpot users reported they didn’t see their APs on the heatmap, while they could clearly see them discovered and listed in the sidebar. This may be caused by visualization configuration. The setting that needs tuning in this case is “AP detection proximity“.
By default, you will only see those APs on the heatmap that have a signal stronger than -60dBm. You may change this using the setting mentioned. If you slide the indicator to the far left position, each and every detected AP will become visible on the map, however, the validity of their positions will be lower, as APs with weaker signals may in fact be located outside the borders of the surveyed area (they may appear on the edge of the heatmap).
The default value of -60dBm was chosen as the majority of APs in real environments have the signal of -40dBm when measured close enough to the AP itself. All lower values are considered to be either outside of the taken sample or belonging to a different floor.