Two of my domains using Argo Tunnel started displaying Error 526 - Invalid SSL certificate today, after working perfectly for weeks. No settings on the Cloudflared dash or the machines themselves have been changed.
In both cases Argo Tunnel successfully connects to port 80 locally (http:127.0.0.1:80) on the two machines serving these two domains. Four other domains connecting to machines on port 443 (a mix of local and remote) are working just fine.
One other difference between these cases is that those instances of Argo Tunnel (cloudflared) that work fine are version 2018.12.1 and those that don’t work are version 2018.7.2. I am unable to upgrade these two as this in the last version that runs on ARM. (All newer versions exit with a segmentation fault error.)
Any help with how to debug this would be appreciated.