I responded to that thread with the solution that worked for me and worked on Don's system.
First off, this is a Roon issue and not a StreamPlayer issue.
I (and a couple of our StreamPlayer customers) had this same problem when upgrading to Roon 1.3.
The first thing is to insure that the core and remotes are all on the same version.
Once you have done this, you might find that under "Settings" and then "Storage" it shows the StreamPlayer "DriveNotReady." If you go through the Add Folder process, you can add this exact same Folder again. When you do, you will probably notice that it immediately starts indexing the music files in that directory. Then you can delete the original folder (the one showing DriveNotReady).
I don't know why it recognizes the added folder but not the original which was exactly the same folder. But, so far at least, this has worked on my StreamPlayer and on Don's as well. It should work for you.
If you have questions, post them here so that if any others are having similar difficulties, the solution will be available to all.