Hi @Darizona - Thanks for reaching out, though we're sorry the cap on your Camelbak Crux is giving you some trouble. Once the cap is flipped over onto the reservoir, make sure it is parallel to the receiving end and that the threads are lined up correctly. Once centered, it should twist into place without needing any special steps. You can also watch this video with a close up view of the process for a better look.
If that is not working correctly and you have had the reservoir for less than a year, then your best bet will be to bring it back to your local REI or to contact our Customer Support Team.
Let us know if you have any further questions. Hopefully this helps!
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