You may have more clients than your Emerald has been
licensed for. Remove the extra clients, or license
your Emerald for the number of clients you need.
The other possibility is that there are two computers
using the same extension. You can find this in the
dialer.ini configuration file. Look for EXTENSION=xxx,
where xxx is the extension. If two different computers
use the same extension, Emerald will keep alternating
between them and eventually run out of licenses.