Hi!
The icon path of the “DEHCCavalryLOSTeamSPC” tech is
ui\techs\hc_team_cavalry_line_of_sight\hc_team_cavalry_line_of_sight_legacy
which means this tech doesn’t have an icon
It should be
ui\techs\hc_team_cavalry_line_of_sight\hc_team_cavalry_line_of_sight_legacy.png
There, I fixed it for you. I know ths game is abandoned, but still, maybe before 2040 we get a last bug fix patch