We sincerely apologize for the inconvenience you are experiencing.
Based on the information you have provided, the issue is most likely related to your server environment. Please note that SP Page Builder 5.6.1 requires PHP 8.0 or later. Since your website is currently running PHP 7.4.33, this version is not compatible with SP Page Builder 5.6.1, which can result in the frontend not rendering properly and backend issues such as the session expiration message.
We kindly recommend upgrading your PHP version to PHP 8.0 or higher and then checking the issue again. Before making the change, please ensure that your Joomla installation and other third-party extensions are also compatible with the newer PHP version.
If the issue persists after upgrading PHP, please let us know, and we'll be happy to assist you further.
Best regards