Troubleshooting iOS and macOS

Products won't load? (Invalid Product ID)

• Have you enabled In-App Purchases for your App ID?
• Do you have a iTunes Paid Application contract in effect?
• Have you checked Cleared for Sale for your product?
• Are there any contracts waiting for approval?
• In-App Purchases have all fields filled (including screenshots)?
• Did you set a price that is not "USD 0 (Free)"?
• Did you wait 24 hours?
• Using a real device (not a simulator)?
• Are you using the full product ID in register?
• Are there any error in your product ID?
• Do you wait cordova's "deviceready" event before loading the purchases?
• Have you submitted (and optionally rejected) your application binary?
• Does your project’s .plist Bundle ID match your App ID?
• Have you generated and installed a new provisioning profile for the new App ID?
• Have you configured your project to code sign using this new provisioning profile?
• Are your bank details active on iTunes Connect?
• Have you tried deleting the app from your device and reinstalling?
• Is your device jailbroken? If so, you need to revert the jailbreak for IAP to work.

I created localized descriptions but it keeps returning the English info.

The returned language depends on the App Store you registered.

ios nsinvalidargument invalid product identifier (null)

Checklist:

• Are there any missing "Contract for Paid Applications"?
  • You need to have a iOS Paid Apps contract in effect for In App Purchase to work.

ios login popup shows multiple times

This might not be your issue, but it's worth knowing that it happens in development, if iTunes is logged in non-sandbox mode (which happens when any other app checks something with iTunes). The same behavior can't happen in prod. It's one of StoreKit's SDK rough edges... I'm not 100% sure you're not facing a more complex issue, but I've seen this one happening more often than not.