This is what the description says about this package:
"Fully custom autopilot systems, with full Cat III auto land, V/S, Managed CLB/DES, OP CLB/DES, heading and NAV modes. VNAV and LNAV included. FPA/TRK included. Steep Approach possible on A318." - Aerosoft.
As you see, the autopilot is supported which means there is something wrong with your FSX installation.
However, I recommend checking the following PDF manual to activate the autopilot. If you still have problems, click on the General forums and post a question to the developers.