When I create a new post, the first block displays, “This block has encountered an error and cannot be previewed.” Why?
Hmm… that’s a new one on me. But you’re definitely not alone! There are many, many people reporting this same error on the WordPress support forum.
It could be that you’re experiencing a conflict with your theme, or an active plugin on your site. If your hosting plan includes a staging server (and if it doesn’t, you should consider moving to a Managed WordPress host that does), you can experiment with disabling your plugins, then re-enabling them one at a time to see which one is causing the error.
Alternatively, you might reach out to the support team at your hosting provider, to see if they’ve encountered similar issues with the particular server configuration that powers your site.
Hopefully, one of those course of action will help you get this resolved ASAP!