The – most likely – cause for this error is a file/directory permission issue, especially if – at some point – you updated plugins directly by using ftp.

For a possible solution have a look at
https://techubber.blogspot.com/2017/09/how-to-fix-wordpress-plugin-update-failed-solutions.html
and generally
https://www.google.com/search?q=Update+Failed%3A+Plugin+update+failed
of course.

Some security plugins will also apply settings that would stop this process to work.
Therefore, if you are using plugins like wordfence or similar, or things like “System Tweaks” in iThemes, try de-activating those (temporarily) and see if the update works then.
(If it does, simply re-activate the aforementioned plugins/settings after your successful update)

If you are using settings in an .htaccess file to restrict siteaccess by implementing some sort of authentication to access your site, disable this authentication requirement then try to update the plugin(s) and subsequently re-enable authentication as appropriate.

If none of that helps, you can also do the following:

(It is always advisable to make a full backup of your site first if things should go wrong for some reason !)

• De-activate the plugin(s) in question but DO NOT UNINSTALL them (if you uninstall, you WILL loose your settings related to the plugin you uninstalled)
• Download the updated/latest versions of the plugin(s) from https://www.wp-pizza.com/my-account/
• Unzip the downloaded update(s) somewhere
• Ftp into your site and simply overwrite the plugin files with the updated ones you unzipped earlier(typically found in [path]/wp-contents/plugins/[plugin-in-question]/[files|dirs to overwrite])
• Note: if you do that you *might* change file permissions/ownership and subsequently get the (same) issue you are having regarding updates – then again as you are using ftp because you already have that issue, it wont change anything really)
• Re-activate the plugin(s) from within the WP dashboard – it will update what needs to be updated