Try deleting the contents of the directory wp-content/plugins/akeebabackupwp/app/tmp/compiled_templates in case you have a stale file in there. Normally these files are regenerated periodically but let's be sure it's not something as simple as that first.
If the problem persists, the real issue is that one of the core files in Akeeba Backup was removed, either accidentally by you or because your host did something without telling you. In this case try the manual installation
method in our documentation to reinstall the files of our plugin. Please do not
complete uninstall the plugin before doing that; you'd lose your settings and existing backups.
If the problem happens again, especially if the software works for a few minutes or days without a problem, you definitely need to talk to your host. Some hosts really do delete files without asking or notifying you
in the name of "security" but as you can read in the linked article it's just a bad idea, executed ever worse by people who wouldn't know security if it came and hit them on the head.