Memberstack coupons look like this:
Note: This feature is for Memberstack subscriptions only and not used for customer coupons.
Here's how to redeem your coupon.
Step 3 → Click on the coupon link.
Step 4 → Select a plan.
Step 5 → You should see a message that says "Coupon applied." If you don't see this message, go back to step 3.
Step 6 → Enter a credit/debit card & complete the checkout.