Can't Generate Promo Codes

After clicking "Generate Codes" in App Store Connect, I get this error:

Can't Generate Promo Codes
We're having trouble generating the codes. Please contact App Store Developer Support for assistance.

I have been getting this message for about a week now. I contacted support but they're taking too long to respond and I'm worried that I'm wasting time and I could be fixing it by myself.

They did escalate the problem, but so far that only meant I had to re-state the problem 3 times to different people, preparing a video walkthrough two different times.

Some details:
  • My app is in "1.0 Pending Developer Release" state.

  • It's a paid app. (Game, actually.)

  • A colleague suggested I should make sure "TestFlight is disabled". I have no idea what it means. I did use TestFlight during development, and I don't think there's a way to "disable" it.

  • The problem happens in both Safari and Chrome. There's nothing in the JavaScript console. I also tried after cleaning all "Website Data" in Safari. No luck.

I'd be grateful for any suggestions.
Can't Generate Promo Codes
 
 
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