Support

It looks like you have a mix of files from different versions. Try installing Akeeba Backup twice in a row, without uninstalling it before or in between.

The thing is, the error message does not make sense unless you have a mixed set of files. Namely, I expect that the plugins/console/akeebabackup/services/provider.php file is updated, but the plugins/console/akeebabackup/src/Extension/AkeebaBackup.php file is not. This is one of two ways PHP can be throwing this error.

Please open the file plugins/console/akeebabackup/src/Extension/AkeebaBackup.php and check line 40. It should read exactly this:

public function setCLICommandFactory(CommandFactoryInterface $factory)

Moreover, please open the file plugins/console/akeebabackup/services/provider.php and check lines 48 to 55. They should read exactly this:

$plugin = version_compare(JVERSION, '5.4.0', 'ge')
    ? new AkeebaBackup($config)
    : new AkeebaBackup(
       $subject, $config
    );

$plugin->setApplication(Factory::getApplication());
$plugin->setCLICommandFactory($container->get(CommandFactoryInterface::class));

If either file's lines are different it means that the plugin –which is part of the installation package– has not been updated properly. Delete the folder plugins/console/akeebabackup and install Akeeba Backup twice in a row, without uninstalling it before or in between. Then check the files again; their contents should be as I described above.

The other reason PHP might be freaking out is if your host has set up PHP's OPcache code cache in a way which does not allow Joomla to reset it when updating an extension. If the files are correct as per the information I gave you above but you still have the exact same problem you stated (the error message MUST be “Attempted to call an undefined method named "setCLICommandFactory" of class "Akeeba\Plugin\Console\AkeebaBackup\Extension\AkeebaBackup".”) then contact your host and ask them to reset OPcache.

To clarify, OPcache can be configured in such a way that your server "remembers" the contents of .php files without reading them again from the storage. This makes your site faster, since PHP does not have to read and parse each .php file being used every time someone accesses a page on your site, or every time you run a CLI script. However, this also means that if the .php files chance, PHP won't know about it (always depending on server configuration!). This is a problem when updating Joomla and extensions; the new code is there, but your server is unaware. At best, you get an immediate error like you have here, alerting you to the problem. At worst, your server still runs an older version of the software with unknown security and stability consequences. Joomla DOES try to tell your server to reset the OPcache for each file it installs during an update BUT it's possible that a bug in Joomla or a configuration setting in your server prevent that from taking effect. That's why I am saying that you may have to ask your host to reset the OPcache.