After investigating the issue, we found that it is related to the account used during the device activation. Allow me to clarify how the transcription quota works:

When a new device is activated, the currently logged-in account automatically receives a 3-month trial of the Professional plan, which includes 1,500 minutes of transcription per month.
After the trial period ends, the account will revert to the Star plan, providing 300 minutes of transcription time per month.

It’s important to note that this benefit is exclusive to the account used during the initial activation. If the device is later bound to a new account, the new account will not receive the 3-month trial or the 300 minutes per month quota, as these benefits have already been allocated to the account that initially activated the device.

This is why you are seeing the "insufficient transcription time" warning on your new account—the transcription quota is tied to the account that initially activated the device, not the new account.