Check whether the SYS:AfA_OS_Libs folder exists and all the libraries are there. If you installed the AfA_OS_Libs folder into different location make an assign AfA_OS_Libs: pointing to the location.
Also the AfA_OS_Loader should be started right after C:AddDataTypes line in your startup-sequence. Then turn off your Amiga and start it again.
Un-install AfA_OS and install PowerIcons instead if it doesn't help.