To run ActiveServer, it's required to have an existing WebMail Pro PHP v8 installation, on the same or a different server, with DAV access configured correctly. Instructions for configuring DAV server can be found at:

Configuring DAV server

After setting up ActiveServer, with or without autodiscover feature, you can check its availability using Remote Connectivity Analyzer from Microsoft. It provides in-depth analyzis of which steps of the connection session were successful and what kind of errors occured.