The mixed content or SSL issue occurs due to having a secure connection and it does not load the style sheet of the website.
Please try to change the website link from HTTP TO HTTPS
For this open your site WP Admin Dashboard and Navigate to Setting >> General and change the WordPress website URL from http:// yourwebiste.com to https://yourwebiste.com
Second way to change this is, Navigate to Dashboard >> Plugins >> Add New.
Search for Really simple SSL plugin in the new plugin search directory and install and activate it.
After Installation click on the top of dashboard you will see the notification showing below and you have to click on go ahead button and finally check back your site after removing the browser cache.
Hope this helps 🙂
Stay Safe & Healthy…