m. subdomain doesnt work

1. created subdomain (m.qubauniversity.com) and pointed to normal domain point (same folder)
2. added these to .htacces(root)
RewriteEngine On
RewriteCond %{HTTP_HOST} ^m\.(.+)$ [NC]
RewriteRule ^(.*)$ https://www.qubauniversity.com/$1 [L,P]

but not working