These are the official directions for testing with sandbox accounts:

1. Set up test user accounts within Users and Roles in iTunes Connect
2. Clear any account information stored on your test device. In settings, go to the Store settings. Click the Sign Out button. (Note that iOS 11 does not have a section named "Store" in the settings. I go into iTunes & App Store and sign out from there)
3. Connect the test device to your Mac.
4. In Xcode, set your test device as your scheme's destination
5. Open your app, and perform your in-app purchase product testing
6. Use your test account credentials to test the purchase.

I have tried following these instructions, but I'm not able to complete step 6. When I launch the app after signing my Apple ID out of the App Store, it asks me to enter the password for my Apple ID. It does not give me the option of entering a different account. I don't see any way to use a sandbox account.

Are Apple's instructions out of date? Should I be doing something differently?

These are the official directions for testing with sandbox accounts:

1. Set up test user accounts within Users and Roles in iTunes Connect
2. Clear any account information stored on your test device. In settings, go to the Store settings. Click the Sign Out button. (Note that iOS 11 does not have a section named "Store" in the settings. I go into iTunes & App Store and sign out from there)
3. Connect the test device to your Mac.
4. In Xcode, set your test device as your scheme's destination
5. Open your app, and perform your in-app purchase product testing
6. Use your test account credentials to test the purchase.

I have tried following these instructions, but I'm not able to complete step 6. When I launch the app after signing my Apple ID out of the App Store, it asks me to enter the password for my Apple ID. It does not give me the option of entering a different account. I don't see any way to use a sandbox account.

Are Apple's instructions out of date? Should I be doing something differently?

Followup note:

It turned out that for whatever reason, trying to use sandbox accounts on my iPod Touch is a lost cause. However, I am able to use sandbox accounts on my iPad Air 2. But another team member is not able to use sandbox accounts on any of his devices, experiencing the same issue I outlined.