I assume that the Netgear switches and the Airport Express are plugged into the H369A. And that internal Roon communication is fine between the Core and the DAC+.
When the Internet Radio stations do not work, did they work before and have stopped, are they new stations you are setting up and they do not work, is there an error message associated?
Things to try:
You might try setting your DNS to use 8.8.8.8 or 1.1.1.1.
Also, you might try putting a non-managed switch in place of the .12 switch to see if the settings on the .12 switch are possibly the issue.
Things to try for Tidal:
Try logging out of Tidal in Roon, rebooting ROCK, and then logging back into Tidal. Also, there is a process for clearing the Tidal cache in Roon. See this post: