If the Lightweight Access Point (LAP) failover does not work, check for the Cisco Access Point (AP) fallback option. The AP returns back to the primary controller only if AP fallback is enabled, located under Controller > General in GUI. Also, all of the controllers that are to join (or failover to) APs must be added to the Mobility Members list on each controller.
In optimal situations, the default time for an AP to join a controller is anywhere from one to two minutes. In addition to this, when there is a Mobility Group setup, the AP does not proceed to another controller until the AP determines that the current Wireless LAN Controller (WLC) is no longer accessible. The default detection time is 30 seconds, which is the interval to which the AP heartbeat is set. This timing can be adjusted down to one second. However, if this was not performed the last time the AP heard from the WLC, the process takes 30 seconds before the AP realizes it is gone. If an AP does not hear from the WLC after this operation is performed on the AP heartbeat seven more times, once per second, it associates to an available controller. This is the default operation.
Note: Controllers that are to service the same APs and clients must use the same Mobility Group name (case sensitive) in order to allow seamless client roaming and AP failover. The only reason to have any controllers in the Static Mobility Group with a different Mobility Group name is for guest networking.