i also had big problems installing csdm mode on rehlds in the past
and i didn't know why it wasn't working properly
on windows it was even worse
the csdm module is not loaded on windows if you have latest rehlds version
i didn't know why then, because i was using the latest version of rehlds
until i tried to downgrade the rehlds version until i could find a compatible version
at the moment, for me, it works properly
tested on amxmodx 1.8.2 (hg60) and 1.8.3 (git5201) | rehlds version 3.8.0.711
however, i did not test on amxmodx 1.9