Thanks for writing in and sharing your report - welcome to the community as well!
Based on your account information, we’re only seeing the Mac, which is running an older version of Roon, Roon 1.8, which isn’t compatible with Roon 2.0 which is likely running on your Nucleus.
Are you able to update the Mac to run Roon 2.0? Or, if you’re not planning on using your Mac with Roon and your new Nucleus, and only want to host your local library on the Mac, we can ignore this.
Based on the screenshot, it looks like your Mac is still running as Roon Server. Here’s more info on setting up shared folders on your Mac to be used over a network share when you’ve switched over to your Nucleus: