Hi - did you follow the steps in the LittleNavMap manual to load the scenery? Is the path to your scenery files correct?
https://www.littlenavmap.org/manuals/littlenavmap/release/2.6/en/SCENERY.html
Microsoft Flight Simulator 2020: The base path of the MSFS installation and its directories Community and Official is detected automatically. You can change the path manually if needed.