Hi Peter
To amend this issue could you try deleting the template html folder (../templates/j51_layla/html/) and then installing your template again via your extensions manager. This will replace the html folder with the correct Joomla 4 version.
If this does not resolve the issue, may I suggest sending temporary administration access to your Joomla installation to
[email protected] and we will examine this issue further. For our reference please paste a link to this post in your email.
Ciaran