There could be a number of reasons why notifications are not working. Here are a few things to consider

1. Notifications for the 4.x series require a minimum Pega platform version of 8.1.3
2. First, ensure that you have followed the instructions for configuring email notifications
3. If you are upgrading from a previous version of Deployment Manager, there are a few additional steps you might have to confirm for configuring email accounts.
4. Ensure that email notifications preferences are set for your operator correctly
5. Ensure that you have the correct email address in your operator record
6. Check to see if you are receiving notifications in the Notification gadget in Deployment Manager portal
7. Notifications will not work if the Stream Service is not running. There are couple of options here to consider
   1. Ensure that the notifications Queue Processor is enabled
      1. This can be fixed by going to Admin Studio portal, then navigate to Resources-->Queue Processors.
      2. Ensure that the queue processor pyProcessNotification is enabled and running
   2. If the previous step did not fix the problem, then the Stream service might need to be restarted
      1. Resolved by starting Stream Service (Dev Studio-->Decisioning-->Infrastructure-->Services-->Stream).
      2. Edit the settings to make sure Replication factor value does not exceed the number of nodes available.
      3. Add Node
8. Notifications will also not work on on nodes with an untyped Node classification. Ensure that the node type is Universal or at the very least Default. On 8.1.x there is a chance that the node type is set to Uptyped which can cause issues with Stream processing which is required for notifications to work properly
9. Ensure that the SendCorr agent is running on at least one node.

This is a frequently asked question about Deployment Manager. Find more answers here.