Hello Henk Nowee,

Sorry for the inconvenience you're experiencing. We've identified the cause of the issue with the page layouts and pre-made blocks thanks to valuable assistance from one of our users. A permanent fix will be included in the upcoming update.

In the meantime, please apply this temporary solution:

Open the file: /components/com_sppagebuilder/helpers/ajax.php

Then, add the following line at line 22:

use Joomla\Filesystem\File;

This should resolve the issue. If this doesn't solve the issue, please reach out and I'll look into it more deeply.

Hope this helps!

Best regards