Hello,
I received a new OSMO Action last weekend. And in the kit included was an additional lens cap.
I saw some youtube videos that it is easy to change the lens caps by turning it counter clockwise.
But the one on my cam does not move.
Any trick or tool needed?
Thanks for advice!
Martin

It is normal it is on very tight, you should be able to find youtube videos on how people got it loose.
Personally i gripped mine with some pliers, with a piece of cloth in between them and the lens cap to not scratch it.
You of course do not want to clamp down on it like a SOB, it is tight but with pliers it come loose easy

Hi Braennborns. Thank you for reaching us regarding the concern and I'm sorry to read and to know that you are having issues regarding with removing the lens cap of your DJI Osmo Action. Please be advised that, if the Osmo Action's lens filter cap is detached and attached poorly, then the waterproof performance will be weakened, water may enter into the camera when it is used underwater, and the lens may fog up, which will blur the image. Besides, the lens may be smeared when detaching the lens filter cap, so please be careful when detaching the сар. To protect the lens, the lens filter cap is firmly attached to the camera. If you cannot remove the cap, then you can use a tool that has protection or a cloth to remove it. Using a metal tool to detach the lens filter cap is not recommended as the cap's surface may be scratched. Please always cover a piece of cloth over the lens filter cap to prevent damage when using a tool.

You can try a couple of thick rubber bands on the lens rim and twist it counter clockwise then the lens should be loosened easily.

I may seem goofy at first, but here's my solution.  I ride road bikes and the tyres have tubes.  Older tubes get 're-purposed' for various uses.  To get a better grip on the lens cap ring I cut a section of tube that was about 15mm wide.  I stretched it over the lens ring and I leave it on after the initial cap removal.  By leaving it on, I can more easily tighten to assure a good seal.