Ok. So the user database is still working correctly, but the XP was lost. I don't see anything actually wrong with the xp save settings. Here is what i have on my own server
set g_XPSave 9
set g_XPSaveMaxAge_xp "30d"
set g_XPSaveMaxAge "30d"
set g_XPDecay 0
set g_XPDecayRate 0.0
set g_XPDecayFloor 0.0
set g_maxXP 10000
set g_damageXP 0
Does it now store XP or is it always resetted when you enter the server. What is the gametype you are using on the server (mapvoting, campaign, ..)?