Launching task fails and the log file returns error "Access refused".
Stop the BGMD Service,
Delete the SPT.hk file located in \Esko\bg_data_fastserver_v100\Tmp on the Automation Engine Server.
Finally restart the BGMD service again.
This is a "house keeping" file that keeps track of files in the Proof Server. It may contain old information from a previous Proof Server running on a different host, which would lead into issues. It is continuously updated while the BGMD service is running, hence the need to stop the service first.