Please take a read through the linked post again, it seems your question is already answered:
Also the blue thread title is a link that will take you there. IIRC your question about the error message is also already answered in that thread. Further questions about the beta package for DSM 7 are better asked in that thread (located in #roon:qnap-synology) instead of here (#support).
Note: I don’t know more about this than what’s already written in that thread as I’m not a Synology user. Support is for Roon support. Question and issues about the NAS packages and accompanying NAS configuration should go to #roon:qnap-synology. You can just add to the existing thread I linked already for your questions about the beta package and it’s use (if not already answered therein).