I don't have this issue but a friend finds that in the far north, LNM doen't show elevation data.

Here is elevation data in lnm on a flight from pabr to pabw.    The second image is what he gets

 

This is what he gets for CYXT to CZST. 

 

 

Maybe he did not install the GLOBE offline elevation data: https://www.littlenavmap.org/manuals/littlenavmap/release/latest/en/GLOBE.html

GLOBE is somewhat coarser, but has worldwide coverage.

Alex