United PR has an answer for you...
Hi everyone.
The issue related to the $100 travel certificates has been remedied and all existing certificates should now work as designed on united.com.
Should you encounter any difficulty after attempting to redeem the certificates on united.com, you may call Web Customer Support at 1-800-589-5582 to have the certificates honored.
As always, please continue to share your feedback with us at united.com/customerservice.
Thank you for your feedback.
United PR