I am upgrading a 3.10 site to 4.4. I have deactivated all extensions prior to upgrade and am activating one extension at a time.
Now I get the error: Call to undefined method Joomla\CMS\Application\AdministratorApplication::isAdmin().
I have followed Brian Teeman's instructions on https://www.youtube.com/watch?v=ZO9nmdsLlFw, but after two changes from isAdmin to isClient('Admin') I get the error: Class "JResponse" not found. The error is related to SP Cookie Consent, but I do not know how I solve the problem.
Could you please help?