For addons having their settings in the Shoptet administration (in the iframe), there used to be a problem with third party cookies in some more security aware browsers. Lost cookies were blocking authorization of eshop admin users. This is now fixed by means of a simplified OAuth mechanism, cookie-less iframes and proxy_pass settings – see Placing the addon settings into Shoptet administration.
In the meantime we were using a hack with a “cookie-fix”, which was based on fact the browsers trusted a domain visited before. There was a dummy URL called before the iframe itself just to put the domain into the browser history. This is now obsolete and we will remove this setting on Tuesday December 7th, 2021. There should be no action necessary on addons side, however you can remove the dummy cookie fix URL from the addon to tidy up.