A network engineer configures VRF-Lite on a PE router (R1) to separate CUSTOMER_A and CUSTOMER_B traffic. Both VRFs use EIGRP AS 100. After configuration, R1 forms EIGRP neighbors with CE routers in CUSTOMER_A but not with CE routers in CUSTOMER_B. The engineer confirms interfaces are up, IP addressing is correct, and the same EIGRP named-mode configuration template was used. Running 'show ip eigrp vrf CUSTOMER_B neighbors' shows no output. Comparing the two VRFs, the CUSTOMER_B interfaces are listed under the correct VRF, but the address-family for CUSTOMER_B under 'router eigrp' has 'autonomous-system' unconfigured. What is the most likely cause of the missing adjacency?