Error in iOS IAP test

I keep getting an error in the IAP test.
If anyone knows the cause and solution, please let me know.

It seems that when I press the purchase button, a form appears asking me to sign in, but I don’t see it. Then an action is performed when an error occurs.

When I check the error code, it returns the code “E_DEVELOPER_ERROR”.
Also, the IAP test type is non-renewable subscription.

I have opened a support ticket, but there is no response at the moment, so I would like to ask for your help here as well.
Thank you very much for your help.

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