This sounds like a Joomla! issue, not an Akeeba Backup one - our code has not even run at this stage. Please try all of the instructions mentioned in our troubleshooting page: https://www.akeebabackup.com/documentation/troubleshooter/abinstallation.html
Please do follow the FTP instructions, even though you already have set it up on your site already, as I think that you have the wrong FTP directory set up in there.
Nicholas K. Dionysopoulos
Lead Developer and Director
π¬π·Greek: native π¬π§English: excellent π«π·French: basic β’ π My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!