Non-www domain redirects to registration page

About to launch this site: https://www.prolifeplanet.com/ as a multi-site and run into a weird redirect issue. When the url is typed into the browser without the preceding www, it adds the www then redirects the visitor to the registration page. This actually happens to any page that’s missing the www. They ALL redirect to the registration page.

https://prolifeplanet.com/ <– clicking that link will also redirect to:
https://www.prolifeplanet.com/register-at-pro-life-planet/

I want it to redirect to the home page if the www is omitted (or corresponding page with the www added)..

This is what I have in the htaccess:

1# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]

# END WordPress

I’m not sure where else to look to fix this. Any ideas?