Cloudflare Tunnels not working with all subdomains

I set up the Cloudflare tunnel docker container on my Unraid system and add public hostnames through the web interface. Everything seems to work fine but the tunnel won’t work with certain subdomains.

These three public hostnames all point to the exact same service, however, only two of them work:

“radarr.domainA” → does not work
“radarr2.domainA” → does work
“radarr.domainB” → does work

This is not the only instance where this happens. I have this happen with a few more subdomains. When it doesn’t work I get the following error in the browser: “DNS_PROBE_POSSIBLE”

Both domains are hosted with Cloudflare and I don’t see any differences in the CNAME between “radarr” and “radarr2”, for example. One just works and the other one doesn’t.

I really don’t know enough on how I could investigate this issue further so any help would be greatly appreciated!

Here is another example, in case it helps:

nzbget.domainB → does NOT work
nzbget2.domainA → does work
nzbget.domainA → does NOT work

So this issue seems to be affecting both of my domains. Sometimes a subdomain works, sometimes it doesn’t. And when one subdomain doesn’t work on Domain A it still MAY work on Domain B. I really don’t understand this.

This actually fixed itself after a while. Perhaps the DNS settings needed to propgate? I have no idea but it suddenly works. Would still be nice to know how to look into issues like this when they arise.


I think I am having the same issue as you. I have a tunnel set up to my docker instance on my synology nas. I have several apps set up on my tuner…some of the subdomains work and direct to the app or service I set up on my zero trust portal….some of the other subdomains when I go to the URL, i get nothing…just a white screen that goes no where…no error message. Was this what you were experiencing?