I have exactly the same issue AND this is not the first time.
Yes I can connect directly to my Qobuz account; I am running Roon 1.8 and YES I rebooted it after the update was complete; AND the DNS settings on my router are set to 8.8.8.8. My Roon Core + is connected by 10GB Ethernet and there are NO ports, services or IP addresses blocked at any point in my network upstream of the Core. I have ~80 Mbps service on my EERO mesh network and Ping 8.0ms.
This is NOT the first time I have had this problem and so I want to know WHY the keeps happening ?
So we can better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
Does local content work okay?