WordPress site lost formatting after update

With WP Rocket, you are using an optimisation plugin that also provides a cache. Empty this cache or deactivate the plugin completely. If it then works again, this commercial plugin is to blame for the behaviour. If you want to continue using it, please contact their support: https://wp-rocket.me/support/ – questions about commercial products are not allowed here in the forum.

This may be a plugin or theme conflict. Please attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.

If you can install plugins, install and activate “Health Check”: https://www.ads-software.com/plugins/health-check/
It will add some additional features under the menu item under Tools > Site Health.
On its troubleshooting tab, you can Enable Troubleshooting Mode. This will disable all plugins, switch to a standard WordPress theme (if available), allow you to turn your plugins on and off and switch between themes, without affecting normal visitors to your site. This allows you to test for various compatibility issues.
There’s a more detailed description about how to use the Health Check plugin and its Troubleshooting Mode at https://make.www.ads-software.com/support/handbook/appendix/troubleshooting-using-the-health-check/

I started to use the Health Check plugin and was able to identify which one I think was disrupting our site (Ultimate Addons for Beaver Builder) but once I switched out of Troubleshooting mode I got this error message:

“There has been a critical error on this website. Please check your site admin email inbox for instructions.”

Any insight?

The reason for the error should be visible in the error log. You can find it in your hosting area. If necessary, the support of your hosting can help you.

Alternatively, you could also enable debugging in WordPress. How to do this is described here: https://www.ads-software.com/support/article/debugging-in-wordpress/ – also here the support of your hosting can help you if necessary to edit the file accordingly.

In both cases you should be able to see what the cause is in the logfile.