One reason that Concept may report an error OLN-801 " Error Opening Loadable File ", is that during the upload of a project from a  CPU containing 984 Ladder Logic, a loadable is encountered that does not reside on the PC .
Concept can and will upload 984LL projects.
If the project contains a loadable like the XMIT block, the loadable file(s) must also be present in the Concept's Global \DAT directory.
It will become necessary to manually place the loadable file into Concept Global DAT directory if it does not already exist there..