Hi,
do the switches recognize the SFPs installed on both sides?
you can check by login the GUI of the switches and see port 27 on both switches.
if yes, then it might be a fiber cable issue, as the transceiver "R9D18A" is SFP+ SR, which usually works on Multi-Mode Fiber cables.
I did previous installation s where i used SR SFPs on Single Mode Cables, but i noticed it is very susceptible to any fiber bad installation or connector termination.
try to get the two switches in the same room, and try to connect them using a 5 meters fiber patch cable, if the connection is up, then it is a fiber cable issue.
i suggest either, pull a new OM3 cable rather than OS2. or replace the transceiver with SPF+ 10G LR like "S0G21A"
Best regards,