How to remove a Shimano Quick-Link?
This is a different link than the Sram type of links. Here is a link to the directions I found that includes the HG-40 Quick link. Hope this helps!

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Chain/SI_0034B_001/SI-0034B-001_13_v1_m56577569830625422.pdf