Cannot use verified Sandbox Account

I have setup and verified a sandbox account for testing. I have received both email and text verification and received the email noting that the account has been enabled for two-factor. Yet I receive the error below on both iOS and macOS devices.

Can someone shed some light on this matter? Thanks! Steve

iTunes Account creation not allowed
This Apple ID cannot be used with the iTunes Store at this time. Please try again later
Cannot use verified Sandbox Account
 
 
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