This happens when you have more than one server installed with the same subscription file mounted. In most cases we have seen people have forgotten about an old demo server that is still running somewhere.
There are two solutions to this issue:
1. Find the old server and uninstall it.
2. If you can not find the old server you have to switch everything to a new subscription
- This includes a new server setup
- Manually adding all users to the new subscription
- Sending out activation emails to all users