phinomenal

Ok, yes, it does appear to be depressed below the threads. 
Try cleaning it with a cotton swab dipped in rubbing alcohol.  Sometimes that is enough to get rid of whatever is causing a pin to stick.  If it doesn't work, then you should be able to get it up with some tweezers or very fine tipped needle nose pliers.  Once you get the pin up, check the Troll without the heatsink.

If those things don't work to get the pin to move up, try a regular sewing needle. Those are very small and may fit between the pin and housing to give you a better chance at prying it up. Be very gentle when you do this because the needle is so small, you risk breaking it if you're too rough.

The RX 510 should be spring loaded thy cleaning it like @Adversarious1 said you may want to try pushing it down also this might help it get unstuck

Thank sir for all the help but I think my pin is stuck quite deep down but I dont know why its work on Hellboy with heatsink but not with Troll

here is the pic


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No, it doesn't necessarily mean your Troll is broken, especially since you say the same thing happens with the Hellboy.  It could be several things but is likely a connection issue of some sore.
Try cleaning the 510 connector on the mod and  Troll to see if that fixes your issue.  
Check to make sure the 510 pin on the mod isn't getting stuck in the "down" position (I have seen this issue with several RX200 series mods).  
Check that your coil(s) are not loose.  
Check to make sure the airflow ring isn't making contact with the coil(s) (this would be causing a short).  
Make sure you are in the correct mode for the type of coil you have on it.  
Make sure your coil resistance isn't too low.  
Make sure the screw on the bottom of the RDA is turned out far enough to be making contact with the 510 pin.
Also, provide pics if possible.  The old saying "a picture is worth a thousand words" is true.  Sometimes people around here can tell what is wrong simply by looking at a picture and one of us may be able to give you a definite answer.
Those are all of the suggestions I have off the top of my head, but I'm sure I'll think of more or someone else will chime in.  People around here are good like that.