Can't enroll replacement printer: "Something went wrong. Please try again later."

[4100EPrintProb]

I'm trying to enroll a replacement printer into my Instant Ink account.  I get the error shown in the screenshots below.  I spent more than 2 hours on the phone with HP Support but they couldn't figure out what to do.  What we tried:

1) Using either the HP Smart on the phone or the PC both give the same error message.  The "Printer" part in the screenshot below never loads.

2) Resetting the printer to factory defaults from the Embedded Web Services, then redoing step (1) and getting the same error.

3) After the call, I even tried HP Secure Delete and redoing the enrollment, but I got the same error.

4) Entering the printer enrollment code directly on the website as a replacement printer gives the error "Your HP+ printer can’t be claimed here. This is a new printer that needs to be set up using the HP Smart software or app." as shown in the screenshot below.

5) Entering the printer enrollment code directly on the website as a new printer also gives the same error "Your HP+ printer can’t be claimed here. This is a new printer that needs to be set up using the HP Smart software or app."

6) Creating a new HP account and attempting to enroll the printer there using the HP Smart gives the same error as in (1).

7) The agent promised a callback, but I'm still waiting for the callback.

Any ideas?

[4100EPrintProb]

As I never received the promised callback, I called in again and spoke with someone from the Instant Ink department who hadn't heard about this problem.  He eventually transferred me to his supervisor, who seemed quite familiar with it and advised me this is a known issue with certain models.  He removed my printer from my Instant Ink account and tried again, and it still didn't work, and he advised that this has to be escalated to a case manager to resolve.  He told me it would take 3 days.  Unfortunately, another 3 days have long passed and I have not heard back with any resolution for this issue.

Is there anyone from HP who can follow through with the promised callbacks and help?