Ensure that you have the correct email address in your operator record
Check to see if you are receiving notifications in the Notification gadget in Deployment Manager portal
Notifications will not work if the Stream Service is not running. There are couple of options here to consider
Ensure that the notifications Queue Processor is enabled
This can be fixed by going to Admin Studio portal, then navigate to Resources-->Queue Processors.
Ensure that the queue processor pyProcessNotification is enabled and running
If the previous step did not fix the problem, then the Stream service might need to be restarted
Resolved by starting Stream Service (Dev Studio-->Decisioning-->Infrastructure-->Services-->Stream).
Edit the settings to make sure Replication factor value does not exceed the number of nodes available.
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
Ensure that the SendCorr agent is running on at least one node.