Hello YoSo,
I took the time and installed a fresh joomla 3.10.11 on my lokal machine and SPPB 4.0.3.
If i try to create a new page I get a PHP Error which could be the reason you are getting a blank page.
Tested with PHP 7.2
syntax error, unexpected ')'
/joom3test/components/com_sppagebuilder/addons/accordion/admin.php:369
With PHP 7.4 and 8.0 the error has disappeared.
Please enable the debug-mode within joomla and try to access the edit page again.
Then you should see an error-report.
Alternatively, you can look in the PHP error log of your web server to see if any error messages were recorded there.
If you do not get an error message, the problem is probably in the frontend code of SPPB 4.0.3.
Support will have to take a look at that.
In this case, I can then unfortunately not help and wish you much success that the problem is found and fixed as soon as possible, so that you can continue to work.
For the debug-mode, you open the backend -> System -> Global Configuration -> System -> Debug System
