I was fighting a very similar problem today, but with a CompactLogix controller. I was able to manually add the closest Ethernet device to RSLinx Enterprise, and then use its IP address as the downstream shortcut. Applications relying on that shortcut would then work OK.
(In this case the actual device was a 1769-L33ERMS rev 28, and I was using 1769-L33ERM rev 20.)
However, if I later went back to the FT Administration Console and then opened up the Communications configuration, RS-Linx Enterprise would automatically start browsing the nework and detect an unknown device at that IP address. It would then replace my manually-added device with an unknown device (yellow question mark). This carried through to the shortcut and broke it.
The workaround that seems effective is to go back to Communications, Stop Browsing, Delete Device, manually Add Device, and repair Shortcut -- all while avoiding a trigger to browse. So it is a very fragile workaround, subject to failing whenever the network is browsed. Unlike with RS-Linx Classic, I could not find a way to turn off "auto browse."
Attempting to install the proper EDS file was not effective as per Ken Roach's description of EDS usage. But I did get the impression from this technote:
Products show Yellow or Gray Question Marks after Upgrade
that if we upgrade to RSLE version 5.51 that it would use the EDS database. Unfortunately this server has only a very limited time window for patching, and FT patches never make the cut.