The APs will discover that the WLC is running a newer code version than they currently possess.
Or reload the backup configuration file: cisco 2500 series wireless controller firmware update
enable upgrade firmware tftp://192.168.1.100/c2500-k9w8-tar.15.0.0-2.JSP The APs will discover that the WLC is
Look for the "Predownload Status" to show "Complete" for all APs. cisco 2500 series wireless controller firmware update
Verify that your current AP models (e.g., Aironet 1600, 2600, 2700, 3700 series) are supported by the target WLC software version. Newer firmware drops support for legacy APs.