what are the possible causes of this?
It means that the web server where the Accelerator is running is configured to deny access. Please check the configuration of the web server.
I have follow-up question on this.
We already set the web server to allow access but client PC still got forbidden access error on flexmonster proxy handshaking. The client PC is accessing the web server via proxy server. That proxy server is granted access to the web server also but still error occurs. Are there any other settings that we need to configure?