We're happy to help and there are a few very common issues people run into!
The simplest issue to check is to make sure there was not a typo when you entered your code. Sometimes this can just be the difference between a 0 and an O. You may be able to copy and paste the code from your voucher to the website coupon box to ensure accuracy.
Another common issue is trying to use the voucher order number as opposed to the redemption code. If you need help finding or confirming your redemption code please check out Groupon's FAQ page for troubleshooting information.
If you're still running into an issue we recommend contacting Groupon to verify your redemption code.