Simple way from system tree= Selct My organization and change to " This group and sub groups option =
>> Then sort with last communciation time, this will helps to see the machines which are not updated the communication from given time.
>> Then, you can check with those machines are reporting to new EPO, by doing wakeup call, if there is no update, you can redeploy the agents for those machines.
Additionally: There is a default query : " MA: Agent Communication Summary"
You can duplicate this query and filter with last communciation for one week or day and more as your requirement.
>> This helps to folder those machines and then it is easier to send wake up call and then confirm those are not reporting to NEW EPO.
I hope this will helps