i believe it should be "gamesd.skprx" and not "gamesd_ux0.skprx". check your file name again.
my config.txt is
# This file is used as an alternative if ux0:tai/config.txt is not found.
# For users plugins, you must refresh taiHEN from HENkaku Settings for
# changes to take place.
# For kernel plugins, you must reboot for changes to take place.
*KERNEL
ur0:tai/gamesd.skprx
ur0:tai/nonpdrm.skprx
ur0:tai/vitabright.skprx
ux0:app/PSPEMUCFW/sce_module/adrenaline_kernel.skprx
# henkaku.skprx is hard-coded to load and is not listed here
*main
# main is a special titleid for SceShell
ur0:tai/henkaku.suprx
ur0:tai/de3.suprx
*NPXS10015
# this is for modifying the version string
ur0:tai/henkaku.suprx
*NPXS10016
# this is for modifying the version string in settings widget
ur0:tai/henkaku.suprx