The last time that a backup was successful was a couple of weeks ago when I was last working on the site.
The site is running Litespeed cache, it was implemented recently but I'm not sure whether it was done before the last backup was made, or after.
I copy the backup files, in 100meg chunks to AmazonS3 on completion. The backup should be around 420meg, but it is not being completed so not being stored in the backup directory locally (or on S3).
There is adequate disk space.
I re-ran the configuration wizard but it didn't make any difference, Ajax 403 is still received. I've tried about 4 times now.
PHP maximum execution time on the host is 90seconds, PHP memory limit is 256.
I also can't apply the update of Akeeba Backup to version 3.0.1 because of Ajax 403 error.
See attached screenshots and log file.