In order to get the Swift Gloomhoof mount in Ardenweald you need to find and repair a broken soulweb. It requires interaction with Elder Gwenna at Glitterfall Basin who requires 10 Lightless Silk. When I click on “I have the materials here” and confirm that I want to give her the 10 Lightless Silk, she casts “webshaping”, but nothing happens. The Lightless Silk is not taken from my bag and I do not obtain the repaired soulweb.
Also the icon used supposedly referencing to Lightless Silk in the pop-up box asking to confirm giving Elder Gwenna the item is not actually the Lightless Silk icon.