If you get this error when opening a project, it may indicate an issue with the Rabbitmq software. The service for this software will need to be restarted:
Local Install:
Open Windows Services console
Locate RabbitMQ, right click and Restart/Start
Retry Application
Network Install:
IT will need to connect to the Server where Rabbitmq is installed
Open Windows Services console
Locate RabbitMQ, right click and Restart/Start
Retry Application
If this does not help or you get the error at a different point, please continue with a support member, and please let them know what you were trying to do when the error occurred as well as attaching the Take-Off log file.