Hi @hebhansen,
Since the issue is present for more than one browsers, please check whether the following steps help or not:
https://wp-staging.com/how-to-fix-the-error-cookies-are-blocked-or-not-supported-by-your-browser/
If the issue is still the same even after the above then it might have to do with the plugins or theme causing a conflict.
You could try checking whether deactivating the plugins as mentioned in this doc help or not:
https://www.ads-software.com/documentation/article/faq-troubleshooting/#how-to-deactivate-all-plugins-when-not-able-to-access-the-administrative-menus
This process does not require access to the Dashboard. Should this action resolve the issue, proceed to reactivate each plugin individually by accessing the WP dashboard to identify the specific cause.
If the issue persists even after deactivating the plugins as mentioned in the doc, then kindly access your server via SFTP, FTP, or utilize the file manager available in your hosting account’s control panel and navigate to the /wp-content/themes/ directory and rename the directory of the currently active theme.
This action will trigger the activation of the default theme, which may help determine if the problem is specific to the theme in use, as theme functions can potentially interfere in a manner similar to plugins.
Please do make sure you have a backup of the website before running such test.
Regards,
Nithin