Below I will break down the 7 reasons why a WordPress Plugin or a theme not installing on a website and some ways to work around these errors.

7 reasons why your plugin or WordPress theme will not be installed

The good thing about these types of WordPress errors is that they are easy to identify. Usually there is an error message that accompanies each failed upload, so there isn't as much troubleshooting with something like this as other WordPress errors. It's just more boring than anything else.

So, here are the most common reasons why your WordPress plugin or theme won't install and what to do about them:

1. The wrong file format has been downloaded

Typically, you'll encounter an installation error when manually uploading a theme or plugin via the Add / Upload option in WordPress (as opposed to installing directly from the WordPress repository):

 

The only plugin or theme files that need to be uploaded to WordPress are zip files.

Before contacting the plugin or theme developer, check that you haven't received the correct file. If it came from your client, maybe they unzipped the folder and gave you what they thought was the right file from the inside out. If it's not from the customer and you don't have the correct records, contact the developer.

2. Files are missing in the zip

Now, let's say you tried uploading a zip file in WordPress, but saw this error message instead:

This means that the files in the folder are not what WordPress expected.

Unzip the folder and check the contents. Is this even the correct zip? Does it contain all the files you would expect from a plugin or theme? You can cross-reference the contents of the folder with the WordPress recommendations for the files that should be included in the package:

• A WordPress plugin package .
• A WordPress Theme Pack .

If you found any missing files, contact the developer for assistance.

3. There is a syntax error

When you buy a WordPress Plugin or a theme from a reputable developer, you shouldn't have to worry about this kind of error.

However, let's say your client was trying to cut corners and save money, and so they found a plugin or an online theme that looked promising. You try to install it in WordPress and you receive a syntax error. It will usually say something about "parsing error" and "syntax error".

This all means that there is something wrong with the code. This error can actually occur if you mistakenly try to edit a theme or plugin after it's installed on your website. However, if you see it during installation, the error lies with the developer.

If you want to check the plugin or theme code for yourself, you might be able to detect and fix the error yourself. Before digging, check in other reported issues with the plugin or theme if there is a support system attached to it (via WordPress or a marketplace).

If there isn't, your safest bet might be to get a new plugin or theme for your client. If you don't trust the developer to code the backend well, this problem may persist with every new update (and you don't want to deal with it).

4. The wrong Zip has been downloaded

This error is one that you are likely to run into with larger, versatile themes. You have received a zip file from your client and in all respects it appears to be in good shape. However, let's say you're going to add the new theme:

Then you see this error:

In reality, the stylesheet is not missing. You probably just downloaded the wrong version of the theme file.

Some developers offer different zip packages for their themes, especially if they include plugins and child themes. Here is an example of how Uncode includes various download options on Themeforest:

While it is essential to have this file complete with all documentation, licenses, plugins, and alternative themes, this file cannot be uploaded into WordPress because it looks like this:

WordPress can unzip the top-level zip file, but it won't be able to browse and unzip the entire contents of the folder. If you want to get your theme then you need to download the appropriate zip file.

5. Memory limits are exceeded

Basically this happens when your PHP memory hosting limit is too low to process the installation.

The error will say something like: "Fatal error: The allowed memory size of _______ bytes has been exhausted ..." If you see this memory error, it is easy to correct.

Log in to your site's control panel and open your preferred file editor: FTP or file manager. In the root directory you will find your wp-config.php file. Click on the edit button and add the following line of code:

define( 'WP_MEMORY_LIMIT', '256M' );

Since the default memory limit is usually 64 MB, it will increase significantly and help you install your new theme or plugin without any problem.