Issues after installation or update

In this article


Can't install or update Smart Slider, receiving a PCLZIP_ERR_BAD_FORMAT error message.

Another possible error message:  Update failed: Download failed. The checksum of the file (4a3b9...) does not match the expected checksum value (23173...).

Possible causes

WordPress + PHP/cURL bug - Problem during update

WordPress uses stream to load files in pieces. This seems to have a bug, possibly due to a PHP or cURL bug, that not all pieces are sent through, and some file parts will get lost. As your zip file becomes corrupted this way, you will get an error message about it. We reported this bug to WordPress, and for now, you could follow one of these solutions:

  • Modify a WordPress core file

    This file:
    \wp-includes\ class-requests.php

    has this code around line 84.:
    const BUFFER_SIZE = 1160;
    Modify this value to anything else, like 1161:
    const BUFFER_SIZE = 1161;

    This will modify the size of the WordPress stream given pieces. This way you can try to update again. With this modification our zip file was always downloaded properly based on our tests.

  • Do an alternative update

    We aren't sure if this problem would come up in the future too, so it is possible, that you are only getting this error with the current Smart Slider version's zip file. If you don't want to modify your WordPress core file right now or you don't have access to it, you could try an alternative update instead, and maybe in the future the PCLZIP_ERR_BAD_FORMAT problem won't come back.

Download issue - Problem during installation

If you wanted to do an installation, so you downloaded a zip file from our website or with the Free version maybe from,it could be, that when our zip file was downloaded something bad happened, and your download didn't worked, producing a zip file with an error. To make sure your zip file doesn't have an error, just try to unzip it into your computer. If that works, the server's unzipping shouldn't have an issue with it, unless the server has a different issue:

License issue - Problem during update

If you are using the Pro version of Smart Slider and your license is not activated on your website, or there is an issue happening which blocks the license connection, then your website won't receive our zip file.

On the Dashboard you should check the Info popup. This writes out "Your license is active" if you have activated the license. If your license is not active, activate it!

There is a very common server problem, which makes licenses not work anymore. So even if your license seems active, continue with the steps of this documentation to test it!

If the license is active, go to the Help center. Under "Possible conflicts" you should press the "Test connection" button. This will show you whether or not there is an issue with the connection.

  • If everything seems fine, go to the next possible cause.
  • But if it isn't fine, check out the "Debug information" error log. A common error message you might find is the "certificate has expired" message. If you see that within your log, check out this documentation. But if you do not see that within your log, contact us and send the log from the"Debug information". We will tell you what you should ask from your server host to fix.
Server's Modsecurity

Your server host might uses a Modsecurity rule, which blocks our zip file for some reason.You should contact your server host and ask them to take a look at their logs. They should see when a Modsecurity rule blocks something and they should be able to figure out the exact source of this issue, and they should turn off that Modsecurity rule. If they aren't sure, just ask them to turn off all Modsecurity rules, and take a look, if the PCLZIP_ERR_BAD_FORMAT still happens.

It's also possible that the Imunify360 is flagging the zip file, so if you have that on your server, ask you host to check that as well.

Server's unzipping program is outdated

The last possible cause of this PCLZIP_ERR_BAD_FORMAT error message is, that your server's unzipping program is outdated or it has an error, and it's not able to unzip our zip file.

You should contact your server host to resolve this error.

Alternative solution

You can use the FTP installation/updating method, where you are unzipping the zip file manually, so your server doesn't have to do it:



This won't fix the PCLZIP_ERR_BAD_FORMAT error, but you won't have to deal with it right now.

PHP Fatal error

Common errors:

  • Fatal error: Class 'N2PluginBase' not found
  • Fatal error: Class 'N2CacheImage' not found

The problem is caused by that installing/updating your Smart Slider 3 didn't worked, some of the files are missing probably because of a server issue. A reinstallation (which is the same as the alternative update) would solve the problem!

You can find instructions in these articles on how to perform an alternative update on WordPress and on Joomla.

JavaScript error

Common JavaScript error TypeError: N2Classes.NextendAnimationManager is not a constructor

The problem is caused by that updating your Smart Slider 3 didn't worked, some of the previous files are still used probably because of a server issue. A reinstallation (which is the same, as the alternative update) would solve the problem!

You can find instructions in these articles on how to perform an alternative update on WordPress and on Joomla.

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