Choosing new .exe does not work for a NAS

I was using WebMod to run a Steam game off a local drive with no issues. I was given a Synology NAS, so I moved the game to the NAS and setup the mapping. When I try to repoint to new NAS location, the mapped drive does not appear in the browse drive , so unable to pick the new exe which now resides on a NAS volume. BTW, the games plays correctly on the NAS from steam