Which version of MediaMonkey (Help > About) and what File Type(s) are the files served as (see in WMP). Check if there is an update for Twonky as it may have already fixed the problem on their side.

MMW4 can cast to DLNA capable clients, MM5 can also cast to Chromecast capable clients.

I'm using WDMyCloud as NAS with Twonky Server installed. When using Windows Media Player, I can "see" and access all the songs (files) (about 70.000) and cast them to my network audio receiver no problem. MM shows the mediaserver WDMyCloud and has the usual sub-tree underneath, however when selecting any of the sub-tree menu (e.g. Album or Artist, etc) it doesn't show any songs. I have checked on all the network settings, UPNP protocol, etc

Really at a loss of why MM wouldn't be able to show the songs on the NAS.

On a different note: would I be able to cast songs through MM to one of my audio network receivers like I can with Windows Media Player?

Thanks much for your help!