Mainstage 3 not finding EXS24 user instruments

When I try to import my custom sampler instruments into EXS24 in Mainstage 3, it doesn't see them. More accurately, they don't show up in EXS24's instrument list. "Refresh menu" doesn't help. The Mainstage concert file and EXS24 instruments folder (correctly named "sampler instruments") are in the same directory. This is the correct way to set things up in Logic when using EXS24- I've been doing it this way for roughly ten years with no issues. How can I get EXS24 to see the %^&*@ing sampler instruments?

Thanks,

Mitchell