First, if you haven't already, make sure your guild is registered to your Discord server.
Next, in order for a DM to be sent successfully, EchoStation needs to be able to match a guild member's ally code to their Discord user. This is made possible by registering their ally code with the EchoStation bot. This must be done for every guild member that you want to receive a DM!
Lastly, make sure to opt in before submitting for assignments!