We had a customer who disconnected the database for workflow about 2 weeks before a migration but left repository access online. So users could enter documents into the system but workflow was not there to process them.

Typically all you have to do is start the workflow service again and the subscriber activities will be waiting in the message queue.

However when they started the services after migrating the host to new hardware, there was nothing in the message queue and only new actions in the repository were being accounted for.

Changing physical hardware on a non-VM would never delete your message queue, does changing the hardware on a VM cause this? Did something else they might have done cause this? How can the message queue be wiped like this?