If you're experiencing difficulties using KWIZ modern apps in your form and seeing the mentioned error message, follow these steps to recover:

1. Click on the settings cogwheel (gear icon) in the top-right corner of your SharePoint site, from     the  dropdown menu, select "Site Information."

2. In the "Site Information" panel, click on "View all Site settings."

3. In the "Site Settings" page, locate and click on "Manage site features."

4.  Look for the "Site Pages" feature in the list, and click  on "Activate".