The XPSMCMER0002 and XPSMCMER0004 internal design don't allow the use of the backplane expansion connector. This is mentioned on the module user guide:
The unit uses the same physical case as the other modules but to avoid confusion, it's supplied with a black label covering the backplane cutout (as shown in attached image).
The unit uses the same physical case as the other modules but to avoid confusion, it's supplied with a black label covering the backplane cutout (as shown in attached image).