The volume used by both systems is not the same physical volume.
System Action: If this message is issued during XCF initialization, the system prompts with messages IXC239A and IXC252D. If it is issued after XCF initialization is complete, the system continues running without access to the named function.
Notify the system programmer. When directed by the system programmer, respond to the IXC252D prompt, if applicable, or issue the SETXCF COUPLE, PCOUPLE command to bring the named function into use.
Make sure all systems are sharing the same physical volume.
Cross System Coupling Facility (SCXCF)
IXCL1AFN
1,2
12