Separate the two problems
Did searching the code fail to show a promotion, or did a coupon fail to reduce the checkout total? These are different steps. For a missing promotion, recheck the code and account. For a rejected coupon, open that coupon’s own conditions and compare them with your current basket.
Use a short diagnostic checklist
Read the expiration, including any displayed timezone. Check whether the offer is limited to particular accounts or regions. Look for product exclusions and minimum-spend conditions. If you changed the basket after choosing a coupon, check the total again. OfferBrief cannot see your account and cannot determine which condition caused the rejection.
When to stop retrying
If the app says you are ineligible or the promotion has expired, repeated searches do not establish eligibility. Contact Temu through its support area if the displayed terms appear to match your order but the coupon is still rejected. Keep the error wording and a screenshot with personal information removed. Confirm the final payable amount before purchasing.