I get the above error message on all meetings - even those I host. Cannot close any meeting even tho I am administrator.
I see you are military, are you using DCO? If so, then you should reach out to the DCO support team, Adobe - Defense Connect Online
If not, I would recommend you start by looking at your Meeting Reports to see what meetings are running and how many people are in them. This can be found by going to the following location in Connect Central; Administration > Account > Reports > Meeting Reports. From there you can see all the active meetings and associate it with your meeeting licensing to see where the issue may be.
As to closing meetings, you must be assigned Host rights to the room and, if on the Named Host licensing model, have a member of the Meeting Host group present in the room to be able to have any functionality for Presenters or Hosts. Do you know if your account is using Named Host or Concurrent User licenses?