CPE get's disconnect message

Hi,

We keep getting this error and I do not know why.
Signal to the client is a -66

00:1E:E5:38:F5:XX@2.4-Omni: connected
00:1E:E5:38:F5:XX@2.4-Omni: disconnected, got deauth: sending station leaving

Does anyone have an idea what is causing this error?
Thanks
Deborah