"List View Web Part could not be added" error when you try to add the Documents List View Web Part in SharePoint Online

Solution:
Open SharePoint designer
Open the page where you are getting error
Edit the page
Click on List and Libraries
Click on Documents
In the Views, click on New
You will get new popup
Enter name. Ex: MyView
If you want to make as Default view, check the option.
Now open Page from SPO
Edit
Add a web part
Click Apps
Categories
Documents
Click Add

Problem solved..