[nikos_a]

Just to clarify, you did not have External Player option enabled in ZDMC?

If so Media Center is having issues with both Windows SMB shares and NFS shares from NAS.

Yes, that's right. But I will try that too. I doubt there will be an issue though because the problem is in the navigation to a certain folder. ZDMC does the navigation right to that folder and allows me to select the files. But out of curiosity, I will do that too and post back. BTW, I have Windows SMB shares (through Windows 10) and it works. At least I tried last night once and didn't have issues. I just had to scan for SMB shares for my PC to appear and I played some files without any issues.

When using ZDMC I can also navigate all my shares, but when it opens the file in Media Center (external player) it just flashes for a quick moment and returns to ZDMC.
I will also try to access shares from a Windows 10 computer. The problem I have is from a Server 2012 R2. But it should not make a difference. I also have a domain, but that should not cause any problems. As I wrote before all my other devices work fine after entering network credentials.

You were absolutely right. I went to ZDMC->Changed to external player->Files->WDMyCloud NFS (this is how I named it)->Went to the folder with movies->Selected to play one

and boom, restart. I did the same process as above and selected WDMyCloud (Samba) and files played correctly. There is a problem here for sure.