Unable to sign in to server

Hello,

I cannot sign in to Plex Media Server on my NAS, it says wrong username/password.

Current setup:
DS216play
DSM SM 6.0.2-8451 Update 9
Plex Media Server 1.3.3.3148

I used a Mac Pro as a Media Server but would like to use NAS for direct stream/play to my TV. So far I haven't been able to setup libraries on the NAS I just installed the app itself.
Should I sign out and uninstall the Media Server from the Mac before proceeding with the NAS?

Thanks for any help.