Error message regarding email address in Developer Support form ("This email address isn’t valid. To update your email address, visit account.apple.com.")

Hello,

I am unable to submit a support request because the Apple Developer Support form displays the following error:

"This email address isn't valid. To update your email address, visit account.apple.com."

My primary Apple Account email address is correct and is already configured as my primary email address.

I have also tested the support form in a private browsing window, but the issue persists.

Could you please investigate why the Developer Support form rejects my primary Apple Account email address?

Thank you for your assistance.