We are upgrading a CICS region from 4.2 to 5.3. When we start the region, ACF2 for CICS Phase 0 initialization completes, but Phase 1 & 2 do not. I've reviewed our setup and cannot find anything obviously wrong. At the same time, however, our sandbox CICS 5.3 region works fine with the same setup. Why would all phases complete successfully in one region and not another?