We believe a recent change to Jira Cloud https://ecosystem.atlassian.net/browse/ACJIRA-1152 has impacted JEMHC's ability to update some issues and generate related notifications.
Historically, JEMHC gained required access to projects through the atlassian-addons-project-access role, but as of 20th Dec appear no longer to be the case. The result of this is that JEMHC 'event' data is very limited, effectively stopping JEMHC having enough data to generate notifications from.
If this impacts your instance, a workaround we have tested is to directly add the JEMHCloud user into each Issue Security Level.
For further updates on this issue, please monitor our live status page: http://status.thepluginpeople.com/
We have identified the root cause and are working on a solution, which will be rolled out as soon as possible.