Hello Yiannosm,
that depends on how you log in, are you using QueueMetrics to do that? Which version are you running?
The idea is that the agents logs in using the QueueMetrics Agent's page, from there they can log into the queues telling QM which extension they have in that moment (for example if they have SIP/537, they should insert 537). QueueMetrics will write an additional log in queue_log (HOTDESK). That will made the hotdesking possible.
Kind Regards
Mirko