DLP activation requires a reboot during the install and then calls the task after reboot to finish up, do the machines autoreboot in their agent policy or are you waiting on users?
pick a machine in epo and choose to look at its client events from the agent context menus
In EPO You want to look for client event 2412 which is a failed deployment, create some reports to look for this generally
Check the McAfee agent logs on the endpoints looking for failed actions
Check the appropriate times in the windows logs for MSI actions and failures and you may also see systems waiting on reboot