You can use the steps below to diagnose WordPress plugin issues.

Prepare your WordPress site for the troubleshooting:

You should always make a backup of your site before performing any troubleshooting. Disable any caching plugins. Disable WP_CACHE if your site uses it.

Look for a plugin-related error:

Enable WordPress debug mode. Visit your site and check to see if there is a PHP error. If there is a PHP error, check to see if the plugins directory is in the file path. Below is an example:

       Parse error: syntax error, unexpected '}' in /home/html/wp-content/plugins
       /basic-plugin/basic-plugin.php on line 50

If the file path contains plugins in it, then this suggests the issue is with the plugin referenced in the error, and you can move on to fixing the issue.

If the error isn't visible on your website, then you'll need to expose the error:

If the detailed errors or logs show a PHP error, then you can begin fixing it.

If you can't locate an error, then you should disable all of your plugins, if you haven't already done so.

Enable the plugins one at a time until the problem or error occurs.

Once an error occurs, then you have likely identified the plugin causing the problem. You can then move on to fixing it.

After confirming the problem is related to your WordPress plugin, you can move on to fix plugin issues in WordPress.