When you are greeted by this error: Error code: SSL_ERROR_INTERNAL_ERROR_ALERT trying to access Cisco WLC via Web GUI, you need remove trustpoint TP-self-signed-X cert, and reenable http server. This will regenerate self signed cert.
C9K5#show run | inc trustpoint TP-self crypto pki trustpoint TP-self-signed-2997515006 C9K5#conf t Enter configuration commands, one per line. End with CNTL/Z. C9K5(config)#no crypto pki trustpoint TP-self-signed-2997515006 % Removing an enrolled trustpoint will destroy all certificates received from the related Certificate Authority. Are you sure you want to do this? [yes/no]: yes % Be sure to ask the CA administrator to revoke your certificates. C9K5(config)#no ip http server C9K5(config)#no ip http secure-server C9K5(config)#ip http server C9K5(config)#ip http secure-server C9K5(config)#ip http authentication local