OSPF adjacency can only be established on the GigabitEthernet0/1 interface. In the router configuration, OSPF is enabled on GigabitEthernet0/1, as indicated by the line protocol being up. The other interfaces, including GigabitEthernet0/0 and GigabitEthernet0/1.40, cannot establish OSPF adjacency due to reasons such as area mismatch or network type discrepancies. References := Implementing and Operating Cisco Service Provider Network Core Technologies