Hi,
I assume rainbow six siege is a game?
A couple of points to check,
1. If you are running multiple scripts simultaneously, there is a possibility of the {Enter} you are trying to send to Rainbow to be captured. I had this issue with one of my ghost scripts which always runs in the background in my laptop.
2. Try adding #Ifwinactive, <Rainbow Something> above the code and see that helps..
3. If the Rainbow and this script run on different accounts, the send key might not work; for example, if the game is running in admin previleges and if the script is in normal previlege.
4. Games usually run in different windows than what they appear to have in title, (example steam games use the steam engine or something else as the main title)..
Please check with the above points, if you still can't run that script, please share the whole script with us and we'll check if the coding is done correct.