On the admin side... When I go to an article, select SP Page Builder for the editor, select Add New Row, click to add a new element, and select Text Block, the editor blanks out. There is no text box shown and there is no longer buttons for "Add New Row", "Import", or "Page Templates". If I had added any elements prior to selecting Text Box, they would be gone as well.
In Google Chrome's Inspector there is an error... Uncaught ReferenceError: tinyMCE is not defined. I had read in other threads that changing the default editor to TinyMCE solved this problem for them... but in my case, it is still happening. When I attempt to add other elements to the row, they are successful. It is only when I try to add "Text Block" that the editor makes everything disappear.