Hi Toufiq,
I've been working with the developer of 4SEO, Yannick, to troubleshoot the issue between Joomshaper/Helix and 4SEO producing this error ""Default Layout file is not exists! Please goto to template manager and create a new layout first" when there is a 404 error.
We have done many tests and concluded that the issue is coming from Joomshaper/Helix template. Testing included deleting the error.php file from the template directory (templates/shaper_helixultimate). When that file is removed and 4SEO's 404 setting is not enabled, the default Joomla 404 page renders. The Joomshaper template displays the Joomla error file instead of its own error.php file, but it still blocks any further rendering.
But when 4SEO's error page is enabled, it renders the message, "Default Layout file is not exists! Please goto to template manager and create a new layout first." Our conclusion is that the Helix template error handling is taking over and breaking 4SEO error page handling.
4SEO's 404 rendering works normally with Cassopiea and all Joomla templates (and all template providers I can think of). Only JoomShaper has been causing this kind of trouble.
How can this be resolved please?
Thanks,
Karen