Magento 1

To avoid problems after installing or updating an extension please follow these steps in the correct order:

  1. Flush all Magento-caches
  2. Reindex all tables
  3. Disable the Magento Compiler
  4. Log out from admin panel, then log in again

Re-installation
If the extension has been uninstalled and is now being re-installed, please check if the database has been cleaned up. In the table core_resource the entry [extensionname]_setup must be removed. Otherwise the install-scripts won't be executed again.


Magento 2

Modules for Magento 2 will usually have a README file in the module package. Follow the instructions from that README file to install the module.


Important

  • Make sure to follow all steps in the correct order.
  • Do not skip any step or CLI command!
  • For a Composer installation, all path names must be 100% correct in the file composer.json
  • When installing from a ZIP / TGZ package, the path to the directory which contains the package must usually be given, not the path to the package itself.


For more details about using Composer, please check this article.