Horrible, horrible customer service. Paid for a Groupon and took an Lyft to Paris to experience this. After standing in a long line, the employee at the desk asked if I had just bought the Groupon to which I said yes. She responded "you can't use it" and then just looked at me like she expected me to just leave. Finally I asked why and she said that they don't honor Groupons purchased less than 1 day ago. I asked her to show me where this was stated as several Yelp reviews reported buying the Groupon right before. She could not find it in the fine print and had to ask her coworker. After a few minutes they did find a line in the fine print saying that the vouchers could not be used the same day. Very poorly written rules since it was written on a separate line than the other restrictions and easy to miss (even the workers missed it initially). Rules are rules, but she was so upsettingly rude about it. Even saying "sorry this isn't valid today" would have gone a long way.
I asked if there was anything I could do and she told me I could buy a ticket. In a later conversation I had with Groupon, I was told she should have allowed me to apply the price I paid for the voucher to the cost of tickets as the price paid for Groupons are essentially like a gift card and always valid; only the promotional value goes away. Instead I left angry. Didn't gamble or visit stores like I planned to. I just got in a Lyft and left Paris. So yeah, my fault I didn't read the rules more thoroughly, but something has to be said for the customer service. Two for one tickets are available in the major Las Vegas guidebooks; presumably accepted without the stupid buy a day in advance rule.