No, the problem is that you’re not resolving one way of accessing your site to your preferred way (everyone has their personal preference for their domain, either with or without the www.)
SO if your preferred site name has the www. then you need to resolve the non-www. to the www. If your preference is to leave it out, then you need to resolve the www. to the non.www.
You do this by modifying your .htaccess file. This is not for the faint at heart and has some danger involved, so if you want to try this on your own, be SURE to backup to your computer your existing .htaccess file first using FTP.
Then, if your FTP client allows you to edit directly into the file on the server, open the .htaccess file and add one of these two commands:
If you want your site to include the https://www.:
RewriteEngine On
RewriteCond %{http_host} ^yourdomain.com
RewriteRule ^(.*) https://www.yourdomain.com/$1 [R=301,L]
Obviously, replace ‘yourdomain.com’ with what your real domain is.
If you want your site to NOT include the https://www.:
RewriteEngine On
RewriteCond %{http_host} ^www\.yourdomain\.com
RewriteRule ^(.*) https://yourdomain.com/$1 [R=301,L]
If your FTP client doesn’t support editing directly then download the file, open it with a plain text editor (not Word) and make the changes and re-upload it. REMEMBER to make a backup copy elsewhere first before you modify it, if all goes to heck you can reupload your backup. OR just delete it entirely, then go to Settings>Permalinks, make a change and click on Save, which will cause WP to regenerate both permalinks and a stock .htaccess file (assuming you’ve made no other changes to .htaccess).
ALSO, if you’re not comfortable with this, call your hosting company’s tech support – they may help you with it.