Compression connectors are designed to have a tight fit with the polycarbonate tubing for a nice rigid connection. In addition, dirt and dust can create friction inside the tube, making it difficult to twist.
First, be sure you are twisting the tube in the right direction. The holes in the tube should move towards the seam between the two halves of the connector. You may have to twist very hard to release the buttons, and continue twisting while pulling to remove the tube. If you can't do this yourself, ask a friend to help: one of you grab the tube with both hands, the other grab the composite shaft, and twist!
Once the tube is out, be sure both the tube and connector are clean. Rub a tiny bit of petroleum jelly, lip-balm, or similar grease inside the tube before putting it back on.
If you have any questions, please feel free to contact us!