Promotional Offer Code Not Accepted on Subscription Plans

I have an Apple subscription with a 2-week introductory offer and a 3-month promotional offer code. There are 2 subscription plans:

1-month subscription 12-month subscription For the 1-month plan, my promotional offer code is "Monthly_Free," and for the 12-month plan, my promotional offer code is "Yearly_Free." However, when users try to enter the respective promo codes for the 1-month or 12-month plans, they receive the following error:

"Offer not available. Your account is not eligible for this offer. You can still subscribe at the regular plan price."

This works fine in the sandbox account, where I can use the promo codes as many times as needed, switching between the 1-month and 12-month plans easily. What could be the issue here?

Promotional Offer Code Not Accepted on Subscription Plans
 
 
Q