I've got FMS15 hosting a database, and have no trouble accessing it using fmnet:// from FMPA15. Also no problem accessing the same host & database using FMPA14. But trying to access the same host, same database from the same machine using FMPA12 fails. Same story using FMPA12 on two different computer. In all cases only one version of FMPA is launched during testing.
Error in FMPA12 is "The file [filename] could not be opened. Either the host is not available, or the file is not available on that host."