You most likely need to upgrade the API dll to a later version. The API appears like any client to the server, and part of the handshake during a login is to make sure that the server and client are compatible. This check is based on the version number of the Client (and server). A "Major" error tells that there is a difference in the second number in the version, like the "48" in the version 1.48.0.18343, indicating a non compatibility situation, where the server and client cannot communicate through the SystemWeaver Client Server protocol.