Support

Are you using Admin Tools' .htaccess Maker? If so, please make sure that the following lines are included in "Allow direct access to these files":

administrator/components/com_akeeba/restore.php
administrator/components/com_admintools/restore.php
administrator/components/com_joomlaupdate/restore.php

I have tested again with Akeeba Backup Professional 3.9.1 on Joomla! 2.5.16 and 3.2.0, it works just fine. I can't see a reason why it wouldn't work on your site, even if you have an older version of Joomla!. At this point I would recommend installing Akeeba Backup Professional 3.9.1 twice in a row, without uninstalling it first, just to make sure that all files are written to the disk correctly. If this doesn't help the only things that could possibly go wrong:

- There could be a Javascript conflict with a third party plugin on the page. We try to perform all sorts of tricks to prevent that, but we can't work around all code of objectionable quality out there. You may want to try disabling a few system plugins from third party developers.

- There could be a .htaccess file or a host firewall preventing access to our restoration script. Unlike Kickstart, the integrated restoration is using encrypted communications to prevent unauthorised use (Kickstart doesn't do that as it's only meant to be a short lived script, deleted right after the restoration of your site). The encrypted request data could be triggering a host firewall as they are something completely out of the ordinary. I have seen that in the past, it takes talking to your host and explaining the use case. For their information, the request is made against administrator/components/com_akeeba/restore.php on your site. This will help them search their logs.