The issue described indicates that authentication requests from the wireless network to the RADIUS server are being dropped. This problem is often due to a mismatch in shared-secret keys between the wireless controller and the RADIUS server. The shared secret is a password-like value that must be configured on both sides to ensure secure communication. By configuring both sides with matching shared-secret keys, it ensures that authentication messages are properly encrypted and decrypted by each party, allowing for successful user connection. References: (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide)