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Troubleshooting the 'This block has encountered an error and cannot be previewed' Message in Formidable Forms

21 threads Sep 16, 2025

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Encountering the error message "This block has encountered an error and cannot be previewed" when trying to embed a Formidable Form can be a frustrating start to your form-building journey. This guide will walk you through the most common causes and the steps to resolve this issue.

What Causes This Error?

This error typically indicates a JavaScript conflict or compatibility issue on your WordPress site. The form builder's interface relies heavily on JavaScript, and when another plugin or theme loads incompatible code, it can break the editor, preventing the form from being previewed or displayed correctly within the block editor.

How to Resolve the "Cannot be previewed" Error

Step 1: Clear All Caches

Before diving into more complex troubleshooting, start by clearing any and all caching on your site. This includes:

  • Your WordPress caching plugin (e.g., WP Rocket, W3 Total Cache). Clear its cache and temporarily disable it for testing.
  • Your browser cache. Do a hard refresh (Ctrl + F5 on Windows, Cmd + Shift + R on Mac) or clear your browsing data.
  • Server-level cache or Content Delivery Network (CDN) cache like Cloudflare. If you use Cloudflare, put it into "Developer Mode" to bypass its cache temporarily.

Step 2: Perform a Conflict Test

The most common fix for this issue is to identify a conflicting plugin or theme. The standard method for this is as follows:

  1. Switch to a Default Theme: Temporarily switch your WordPress theme to a default Twenty Twenty series theme (e.g., Twenty Twenty-Four). See if the form preview works with the default theme.
  2. Deactivate All Plugins: If the issue persists, deactivate all plugins except Formidable Forms.
  3. Reactivate One-by-One: If the form preview works, reactivate your other plugins one by one, checking the form editor after each activation. This will help you identify which plugin is causing the conflict.

This process, often referred to as a conflict test, is the most reliable way to pinpoint the source of the problem. According to sample support threads, the Formidable Forms team frequently suggests this as a first step for unique, hard-to-reproduce errors like this one.

Step 3: Check for Known Issues

While the conflict test is the best approach, some users have reported that specific security plugins, like Wordfence, can sometimes interfere with admin functionality. If you use a security or firewall plugin, check its logs to see if it is blocking any actions from the Formidable Forms plugin and adjust its settings accordingly.

When to Seek Further Help

If you have gone through all the steps above and the issue persists, the problem may be more complex. The next step is to provide as much information as possible to the community or official support channels. Be prepared to share:

  • The exact steps to reproduce the issue.
  • A list of your active plugins and your theme.
  • Any error messages visible in your browser's JavaScript console (you can learn how to open the console here).

By systematically working through these potential causes, you can usually identify and resolve the conflict that is preventing your Formidable Form from previewing correctly.

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