Notification mail sending issues

We have a problem, when we want to send notification to some users (for example you are late to…)… system doesn’t do it (long time there was everything ok and one day this issue happened) (in “Editorial history” we see only that Notification sent to users", but there you can’t find any mail to see like it was earlier and of course after contacting receiver we know - they did’nt receive it).
First of all we contacted with hosting server provider, but they said, that there were no changes last half year.
We receive mail from system about new submissions, and that means mail service configuration is ok.
Any help?

Hi @wegisss,

Have you upgraded the OJS meanwhile? From the explanation I would say you are having problems with scheduled tasks. Search forum for solution.

Regards, Primož