When your referred friends click the referral link, they are brought to a landing page with a coupon code for them to use at your store. If the coupon has expired, the landing page will display a message to let them know that the coupon has expired. You can reset the expiry date of the friend offer by going to your campaign's Friend Offer page.
A sample of a friend landing page with an expired coupon is shown below.
After updating the expiry date / incentive of the Friend Offer, your advocates' referral links will automatically redirect to the friend landing page with the most current Friend Offer incentive you've set.