Not sure what you're seeing but mine is set to 5 minutes and 20 changes (I work slower than Bapu

) and it is definitely working here.
Are you opening the right file? It creates a copy called "Copy
of your file name" it doesn't save into the original file at all (despite popular belief) so if you are opening that it won't appear anything has been saved.
HTH
EDIT: Just another thought, it won't save while the transport is running either so if you've been looping for 5 hours solid

and it crashed there won't be an autosave copy.