Hi there!
When moving an existing Joomla site from one framework/template to another, you should first install the new JoomShaper template and create a duplicate template style for testing if needed.
The "Default Layout file is not exists!" error usually appears when the homepage is still assigned to the old template while other menu items are already using the new JoomShaper template. Since Joomla uses the homepage template style as the default reference, layout conflicts can occur.
To avoid this issue, please follow this order:
- Install and enable the new JoomShaper template
- Assign the JoomShaper template style as the default/Home template first
- Rebuild or migrate the homepage content
- Then assign the new template style to the remaining menu items one by one
This should prevent the layout error from appearing while transitioning between frameworks.
If the error persists, then-
Check Menu Assignments: If you use multiple template styles, ensure they are correctly assigned to your menu items. Try removing all selections in the Menu Assignment tab, saving, and then re-selecting the required pages.
Try the whole process on your local with a full site backup would be a wise decision I think.
Best regards,