The Delaware code says the expiration date of 5/31 is not observed if you have submitted your renewal by the proper date. One must realize that the more permits that are issued, the longer it takes to renew them. Likely a lot of state offices that have been closed or shorthanded due to the Covid that is going to slow everything down. They can't process in a timely fashion without a full staff.
If you were late submitting your application for renewal, you may have to start all over again from scratch, but that's on you, not them.