Contact Apple Support:
Normally, you would go to an Apple Store, setting up a Genius Bar Appointment to take place there, bringing along a death certificate. But, with the Coronavirus Pandemic going around, many Apple Stores are closed at the moment. So, contact Apple Support, asking them how to proceed with this.
Apple Support Info:
Ask to speak with the Apple Store staff. They'll run you through the fix.
Contact Apple:
Why the Wait:
Due to the Coronavirus Pandemic, calls and chats are taking a bit longer to get through. And, that makes sense, because many are at home working out-of-the-house or are taking classes over-the-web, this they have more time on their hands to contact Apple Support. So, it might take a bit to get through to Apple Support. But, just stay on the line, and someone will be with you. :)