Hello, @jmayer
Welcome to DocuSign Community!
Yes, Delegation works in the Dev (sandbox) account, aka, Demo account.
Be sure about the Start Date when setting a delegate, the delegate must be an user who can sign (Sender Profile) and if the notifications are not going to his/her SPAM folder because sometimes a few SPAM filters send to the SPAM folder because the email domain is from our Dev account environment
Also, check with the delegated user is he/she has uncheck some emails notifications in their profile, each user can do that through My Preferences.
Check the envelope’s history, you should see an entry showing the notification sent to the delegate.
I have a Demo account, it works normally.
I hope that helps!
Best,
Alexandre