Is anyone else having a DUNS # problem enrolling as a developer?

I have been trying to register for my non-profit organization and looked up our DUNS number, but the enrollment site won't accept it as valid. I have verified both my organization name and the DUNS # are entered exactly correct. It keeps giving me the error:

This organization could not be verified as a legal entity. If you are a sole proprietorship/single person company, enroll as an individual. If this organization should be listed as a legal entity, update your D&B profile.

When I follow the link to "update you D&B profile" I get an error page that says:

You are not eligible to request an update to your D-U-N-S information.

In order to request an update, you must be in the process of enrolling in an Apple Developer Program.

I AM in the process of enrolling in the Apple Developer Program! I have logged 3 support request calls with Apple through their "Contact Support" page - 2 for phone response, 1 for email response - and none have been responded to by Apple (despite showing a wait time of "less than 1 minute").

Has anyone else experienced this issue and know of a solution?