The most popular problems with installing an extension by Extension Installer in OpenCart 2.x
There are a number of key problems which can lead to errors during installation by Extension Installer in OpenCart 2.x admin panel. Below in this article we will consider ways to solve it.
1. The most common problem during an extension installation process is related to incorrect FTP settings. Before upload an archive with extension you need to set FTP details System -> Settings -> Default Srore -> Edit -> FTP Tab then check Yes option to enable FTP and click Save button at the top right corner of the page to apply these settings. Information about how to get FTP access details you will find at this link.
You can check your FTP access details with some FTP-client program like FileZilla.
2. It is not uncommon for OpenCart users to receive an error "Could not connect as ..." while uploading extension files through the Extension installer. This can be connected with incorrect FTP Host but most often this is due to a disabled FTP access from your hosting provider or FTP settings in general. To solve the problem with disabled FTP there are many free extensions in the opencart marketplace.
3. If you get the error message "Modification ... is using the same ID code as the one you are trying to upload!" during reinstallation an extension this means a previous modification file already exists in your modification list Extensions -> Modifications and you need to remove it.