This plugin won't wor for amxx 1.6, you have to upgrade, go to the amxx website (
http://www.amxmodx.org/). I would suggest delete verything, keep your config files and sma files (on a different folder), then upload new amxx and copy all your configs over (settings only, not the actual files), then start the sma compile, then upload the compiled plugins to the plugins folder and your done.
Helpful guide:
http://wiki.amxmodx.org/index.php/Upgrading_AMX_Mod_X