WordPress is constantly getting upgraded and improved. In WordPress 5.5 (released August 11th, 2020) your site gets new improvements in three major areas: speed, search, and security. Lazy loading is now included which helps speed up website load time. Sitemaps are now automatically included within WordPress itself; not needing an extra plugin for that and helping the search engines better read your website structure. For potential added security benefit; many plugins can now be set to automatically update (if individually available). This is a trickier one though. You probably should not set all of your plugins and themes to auto update if you don’t have the ability to fix something yourself when things fail.
Also, a helpful tip for many. If your website software isn’t being managed and updated by a profession who is able to test updates remotely before applying them; you may have just ran into a software compatibility issue causing your website to not load properly. If that is your case, it could be that your theme or one of your plugins is still in need of an older bit of code that is no longer included by default within the latest WordPress version 5.5. This missing code I am referring to is jQuery Migrate. To add back this script you can install the Enable jQuery Migrate Helper plugin. Of course before doing anything always have a recent backup of your site files and database, and the means to be able to restore that backup.
If that isn’t the fix. You may want to simply downgrade your WordPress version to the last one before v5.5 which is v5.4.2. There is a helpful plugin that many are using to do just this. It is the WP Downgrade plugin.
I hope that helps a few of you. Of course learning all of this is time consuming. It may be the best use of your time simply to get a professional to track and implement you website software updates in the background so you don’t have to think or worry about it.