Have you successfully located and enabled the UPnP or NAT-PMP settings in your router's web UI?
· I've turned UPnP/ NAT-PMP on and ARC won't connect
Select the Diagnostic Keyword or Text String
· Something else
Don't give up yet.
· I'm stuck. I'd like to create a post to ask Roon Community for help.
Describe the issue
Roon ARC was working normally but then stopped working, just shows Not Ready when testing in Roon client. The error code shows: { "ipv4_connectivity": {"status":"NetworkError","status_code":526,"error":"error code: 526"}, "external_ip": {"actual_external_ip":"174.ddd.eee.fff","actual_external_ipv6":"null","router_external_ip":"174.ddd.eee.fff"}, "natpmp_autoconfig": {"status":"NotFound"}, "upnp_autoconfig": {"status":"NotFound"}, "multinat_autoconfig": {"status":"Success","error":"No Error","routers":1,"routers_mapped":1} }
Describe your network setup
I'm using CenturyLink with a Xyxel C3000Z router connected a Casa Systems Fttb fiber ONT with Ethernet. I am running Roon Server on a 2020 iMac with macOS 26.2 installed.
I have checked that port forwarding is setup on port 5500 for my server which has a static IP (this was setup previously and working fine for 6 months)
Thank you for reaching out and providing such detailed information about your network setup. The diagnostic code you shared (status_code: 526) is very helpful.
Error 526 is a Cloudflare-specific error indicating an “Invalid SSL Certificate.” Since Roon ARC relies on Cloudflare’s infrastructure to establish a secure connection, there are two main reasons this usually happens.
1. Recent Cloudflare Outage (Please test again) There was a widespread Cloudflare outage earlier today that affected SSL handshakes in certain regions, which perfectly aligns with the error you are seeing. The good news is that Cloudflare has resolved this issue.
Next Step: Could you please try testing your ARC connection again in the Roon client? It is likely that the issue has resolved itself now that the outage is over.
2. Local Network Security Settings (If the issue persists) If ARC is still showing "Not Ready" with the same 526 error, it means something on your local network is intercepting the secure traffic and replacing the SSL certificate. Since you haven't changed your Port Forwarding settings, this is usually caused by an automatic router firmware update or a built-in security feature.
Check Router Security: Please log into your Zyxel C3000Z web interface and look for any settings related to "Cyber Security," "Advanced Security," or "Web Protection" (ISPs like CenturyLink sometimes enable these automatically). Try temporarily disabling these features to see if ARC connects.
Verify Static IP: Double-check your iMac's current local IP address in macOS Network settings. Sometimes, even with a static IP setup, a machine might grab a different address (e.g., switching from Ethernet to Wi-Fi), meaning your Port forwarding rule is no longer pointing to the correct device.
Please let me know if ARC connects after the Cloudflare fix.
I had similar issues this morning with AT&T fiber modem. It seems my modem won’t let me direct the IP passthrough to my external gateway. I’ve had no issues for over a year. Since the beginning of February, I’ve had many issues with Roon ARC. I’m running Roon on my Windows PC. Usually a reboot of the machine fixes it.
It seems something with the AT&T modem has changed on me. I’ll try rebooting when I get home this afternoon. The issue may have been started by Cloudfare outage. I’ve had my modem reset itself before as well. I had the modem pointing at the external gateway. The gateway forwards everything it receives to my PC which is a static address.
Thanks for your patience while we looked into this.
I’m following up with an update regarding the connectivity issues you were experiencing. The problem was indeed on our end—our system experienced an issue with an expired SSL certificate, which temporarily interrupted secure communication for Roon ARC.
The good news is that our team has resolved this, and the certificates have been fully updated.
Your access to Roon ARC should now be restored. (Note: You may need to completely close and restart the ARC app on your device to establish a fresh connection).
Could you please give it a quick test and confirm if everything is working normally for you again?
Thanks for confirmation. I’ll will work on this when I get home this afternoon and let you know. I need to fix the settings on my modem as I started messing around with them thinking it was caused by AT&T as they have wiped out all my settings in the past.
Yes, I checked again this morning and ARC was showing ready. The issue had been going on for over a week so I hadn’t suspected ban external issue. I had rebooted my modem and OST multiple times and checked settings on the modem over and over. My ISPs DNS has had issues with reliability in the past so I was going to contact them but ARC was the only service affected.