Refer to the exhibit.

The issue with Router 1 missing the route for Router 2’s loopback 0 is likely due to the routers being configured in different OSPF areas. For OSPF to properly exchange routing information, routers within the same network should be configured in the same area. Therefore, the engineer should change the area numbers on Router 1 and Router 2 to be the same, ensuring they can exchange routes, including the route for Router 2’s loopback 0.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) documentation and study materials.