Second Installation in Sub-domain, Single Database

I am trying to copy an existing install at https://www.website.com/ to https://en.website.com/. I intend to do this using a single database.

I created the subdomain en.website.com and it shows up in my FTP client.

I then proceeded to copy all of the files from the root (original install) into the en.website.com subdomain folder and changed the wp-config.php database prefix from $table_prefix = ‘wp_’; to $table_prefix = ‘en_’;

I then went to https://en.website.com/wp-admin/install.php and now I can see the dashboard. However, the dashboard is essentially bare and gives me no menu to edit anything other than my profile.

Where have I gone wrong?

Thank you in advance.
Michael