OpenCart Community

Windows 10, opencart 3.0.2.0

I have just installed OpenCart on my webhost server in public_html. I can open the website with the OC dummy data www.bgarts.co.uk but I cannot open the admin login page www.bgarts.co.uk/admin, I get this error message
Fatal error: Call to a member function link() on null in /home/bgartglk/public_html/admin/controller/error/not_found.php on line 12
and I have no idea what to do, can anyone please help me.
Thank you
Duncan

You are either using an SEO extension, your config.php and admin/config.php files contains invalid paths or you are missing files due to FTP uploaded files rather than uploading the OC ZIP file on your host's file manager console and using the extract button.