V-Ray Light Gen Confusion

My understanding is that if I wish to use my own .hdr, or .exr files for the generation of an exterior lightset, I should be able to check to box for “use custom HDR set” and specify a path to the folder where those files reside. When I do that, to either my own folder of hdr’s, or the one that comes with V-Ray, no files are available for selection. what am I doing wrong, or misunderstanding?