We have email notifications for various actions such as the creation of new tickets to add notes. There is a specific one for the assignment of tickets. 

Please navigate to Admin -> Email notifications -> Agent notifications and check if "Ticket is assigned to agent" is toggled on. If it is and you haven't received them - kindly check with other agents if this issue is recreating for them. For further assistance on the same, kindly write to support@freshdesk.com and we would be able to troubleshoot this further.