I recently ran across and issue where our notification subscriptions were getting disabled every 30 minutes.  The strange thing was that only about half of our subscriptions were being disabled and they were the same subscriptions every time.  I tried re-enabling them with both with Powshell as well as the GUI and had the same result, subscriptions kept being disabled.  After digging through event logs I found this warning.
 

Log Name:      Operations Manager
Source:        Health Service Modules
Event ID:      11452
Task Category: None
Level:         Warning
 

Validate alert subscription data source module encountered an alert subscription data source with configuration that has gone out of scope. Disabling the alert subscription data source module.

Alert subscription name: Subscriptionaca6a276_e5a9_446b_9751_0ea539168e41

One or more workflows were affected by this. 
Workflow name: Microsoft.SystemCenter.ValidateAlertSubscription

The problem turned out to be that we recently cleaned up the SCOM Admins user group.  One of the users removed from the group had created half of the subscriptions.  By putting the user back in the SCOM Admins group and re-enabling the subscriptions the problem was solved.  But we really didn’t want this user in the SCOM Admins group as he had moved on to a different role. 

So why was this happening?    When a subscription is created the user who created the subscriptions SID is associated with that subscription.  There is a workflow that checks every half hour for SIDs no longer valid.  They could be invalid because their accounts access that had been removed, or possibly because the account has been disabled or deleted.

To fix it long term I had to export the “Microsoft.SystemCenter.Notifications.Internal” management pack.  This management pack is unsealed and contains all subscriptions.

Inside the management pack I searched for one of the subscriptions that were being disabled and one that was wasn’t.  I then replaced the SID of the bad subscription with the SID of the good subscription.

After doing replacing the SIDs I re-imported the management pack and re-enabled all subscriptions and the problem was solved for good.

Here is an example of one of the SIDs I had to replace.