Language negotiation only working when logged in

Hello,

I have a multilingual site. The detection method is set to URL → Browser → Default. When going to https://example.com/ while logged in it correctly sends me to https://example.com/es or /de or whatever language my browser is set to. However, when doing the same thing not logged in – so the way most people will encounter the site – it shows the default language no matter what.

Is there a setting or permission that I am missing?

Many thanks!