I was having the same issue as, I suspected it is a DNS resolution issue. Restart your router and also try and ping it from the console to confirm you can resolve to the address
Yes, I was trying to reboot router, supervisor and the whole Pi. Same results. And even as I wrote - traceroute to the same site works from terminal/ssh plugin. Any thoughts?
Can you log into the base device via SSH and confirm if the traceroute/ping works from there as well… I had resolution from within Hassio, but not from the underlying Linux, once I had resolution working from there, it worked fine. I suspect it is using Curl from the underlying OS to do the query. I may be wrong, but that’s what fixed it for me.
I’m using a pure hassio installation on RPI4. I don’t think there is “underlying linux” or any other system. And I’m using a “Terminal & SSH add-on” to get a command line.