First read this:
Follow the guide until you determine which system on your network is the master browser. If you are using a NAS you should make sure that the NAS is the maser browser.
For me powering down, unplugging and restarting the master browser device solved the problem.
One thing that can complicate the diagnostic is that in some cases the master browser designation can bounce around to different devices depending on the order of power-up. Make sure that the NAS or other file server device has the master browser designation.
I spent a lot of time working through router parameters and so forth, probably several hours of diagnostics. Ultimately my NAS was the master browser and when i powered it down and rebooted suddenly the windows shares were visible and usable again.
This is the first time I’ve seen this issue in over a year of using the WD TV.
Anyway, just wanted to share what worked for me.