I'm sorry to hear that your game is crashing when you attempt to launch it. Please make sure that your PC meets minimum system requirements[support.ubi.com], as not meeting those requirements could cause a black screen. Another consideration is that if you are on a laptop your system may be using the wrong graphics card[support.ubi.com].

If you would like to do troubleshooting for this issue, please perform the steps in our PC crashing FAQ[support.ubi.com]. They are very likely to help, and I highly recommend them.

Finally, I can only suggest that you reach out to the vendor from whom you purchased Rainbow Six Siege if you desire a refund.