ERR_INVALID_RESPONSE for a single website, Opera only

macfreek

macfreek

Hi,

When I try to visit https://zenodo.org/, Opera desktop displays an error message:

This site can’t be reached

The web page at https://zenodo.org/ might be temporarily down or it may have moved permanently to a new web address.
ERR_INVALID_RESPONSE

I had no problem accessing the website earlier, and I can still access it perfectly fine with other browsers such as Chrome, Firefox or Safari on my Mac, Opera on my mobile, or Edge on my PC. Other websites work fine with Opera.

I tried Opera on three computers (a Mac desktop, Mac laptop and Windows desktop) and got the same result.

A bit surprised by this result, I tried the following remedies:

Open the page in a Private Window.
Clear DNS cache in Opera: "Clear host cache" at opera://net-internals/#dns
Clear DNS cache on my Mac: "sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder"
"Flush socket pools" at opera://net-internals/#sockets
Delete cookies and site data for zenodo.org
Delete all cookies and site data
Used a VPN to use a different network path
Used my phone as a hotspot instead of wifi, so I'm sure it is not network related.
In Developer Tools, select "Disable cache" and reload with Command-Option-R, ensure this is not a cached problem.
Reboot my computer and try again.
Install a mayor OS update (to MacOS 26.3.1) and try again.

Unfortunately, the error message remains.

Can you access the website just fine?

Is there some good explanation what "ERR_INVALID_RESPONSE"? Is this indicative of a network connection problem, a handshake failure for TCP or QUIC, or does the server not return a proper response?

Do you have any other suggestions what I can do to remedy?

My config (on the machine I did most tests):

Opera One(version: 127.0.5778.76) (arm64)
System: macOS Version 15.7.4 (Build 24G517), later also 26.3.1
Chromium version:143.0.7499.194