How to fix the 'Could not find an XML setup file' error in Joomla!?

This error message could pop-up when trying to install various Joomla! extensions. It could occur when installing components, modules, plugins or additional templates. The general meaning of the error message is that the extension file is corrupted but there are two common reasons that could cause such issues.

1. If you are trying to install archived extension there might be a problem with the zip on your hosting server. As a possible resolution you can do the following:

Extract the archive locally on your machine and upload it to your hosting server via FTP. Then use the option to install the extension from a directory on the server. You can select that via the standard Install extension interface in Joomla!.

Note that this cannot happen on SiteGround servers as zip is installed and working properly on all servers.

2. The extension package is corrupted or incomplete. If you were not able to install the extension following the instructions provided above this is the most probable cause. Thus, it is advisable to not try using the package at all.