Refer to the exhibit. An access point joins the secondary wireless controller but not the primary wireless controller. Another access point has joined the controller and is working fine. The network…

Missing spanning tree configuration on trunk ports is unlikely to be the sole cause if another AP is working fine and basic ping connectivity exists.

If the EtherChannel (port channel) configuration between the primary wireless controller and the switch is incorrect, it can lead to issues where APs cannot properly establish CAPWAP tunnels, even if basic ping connectivity exists over individual links, preventing the AP from joining. An incorrect EtherChannel could manifest as a link not being fully operational or not allowing the correct control plane traffic needed for APs to join.

Incorrect negotiation protocol for port channels would prevent the EtherChannel from forming correctly, which is a symptom of an overall incorrect EtherChannel configuration, not a distinct root cause in this context.

An incorrect trunk port configuration usually means incorrect VLANs allowed or native VLAN mismatch, which would typically affect all APs or cause broader connectivity issues, contradicting the fact that another AP is working fine.