Map shows gray dot for "Fine Particulate Light Scattering"

Looking through all of the map options, I noticed today that my and several other sensors show as a gray dot/circle for the “Fine Particulate Light Scattering” reading. Screenshot shows other area sensors reporting values.

I can’t find anything on this Community or in the FAQ to explain why this value would not be displayed. Ideas?

All other values for my - and the other gray/grey - sensors display fine.