As a Published Artist, you receive a free Platinum Club+ Membership. If you are set up for automatic payments for your current Platinum Club Membership you will need to go into your account and remove your Credit Card information from the site.
You will receive automatic warnings telling you that your membership is about to expire. Ignore these warnings. Once the system has "expired" your membership, you can put your payment info back into your account.
If you are a PA and are not receiving the discounts, you will need to send screenshots of your cart with the Platinum Club discount not applied to firstname.lastname@example.org.