Thanks Juraj for your quick response!
We are using Kentico 12 version and we recently upgraded to hotfix version 12.0.92. This Maintenance is more of patching kind of task.
Along with 'Send Queued emails' scheduled task - "Remove expired sessions" and "Report Subscription Sender" tasks have next run time showing in past too.
When we click the play button to run the task manually, it didn't work, also didn't set correct next run time.
We had to click Restart Application button on Systems page, to resolve this issue.
Also, we got event log with below error:
Unexpected exception occurred while processing activities.
Message: Unable to access availability database 'DB_Name' because the database replica is not in the PRIMARY or SECONDARY role. Connections to an availability database is permitted only when the database replica is in the PRIMARY or SECONDARY role. Try the operation again later.
Exception type: System.Data.SqlClient.SqlException
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout......
We just want to find some other resolution, where we don't have to restart Application explicitly.