Stale job in queue


I have SuiteCRM installed on ubuntu which I have inherited from a previous IT person.
Yesterday we had and internet issue which we noticed had caused the
Check Inbound Mailboxes schedule to stop working.
Looking at the job log it showed the last item to be running for over 3 hr’s
I followed this post and cleared the jobs.
Purging Scheduler Job Logs - SuiteCRM Forum - English Language / SuiteCRM General Discussion - SuiteCRM
As well as manually running php -f cron.php, also running the function::cleanJobQueue, also letting it run at its normal time.
the Check Inbound Mailboxes shows no activity, So I created a new Scheduler to check emails and this is running but so far (over 12 hr) it runs but no new emails are processed.
Please may I have some advice on what I should be checking or the correct logs to gather/review/.

Many thanks

Ok the plot thickens,
So looking at the logs it seems the new Scheduler to check the external mailbox is failing on authentication.
when I check the settings it is using non-ssl (and the none ssl port).
I try to change this and it will not save.
could this be the fact the old job is holding the 993 port open so the new job cannot use it?
If so how do I clear this?