Hello, Gerd. Thank you for sharing your Add-ons list. "DuckDuckGo Privacy Essentials" is also a content blocker. You can try using its toolbar button to make an exception for the site complaining about blocking and see whether that makes any difference. Note: this button might be on the Extensions button drop-down: [[Manage your extensions using the extensions button in the toolbar]]. If that does not help, the problem could be Firefox's Tracking Protection feature. It is also possible to make a site exception for this feature. Click the shield icon at the left end of the address bar (next to the lock). On drop-down panel, at the top, click the slider switch to turn off Tracking Protection. Firefox should reload the page. Did either of those make a difference?