No write access to destination

I'm getting a message "No write access to destination" when I try and record to DVR. I never got this to work, the only thing to note is I installed Plex from the native Synology interface, but then uninstalled and reinstalled manually as the 64bit app. The plex user has read/write in the synology interface. What else can I check?

I have a DS216+, HDextend, lastest plex 64bit.