Compatibility is the key. We have around 100 keyboards (some from Massdrop) and more than 100 mice (not all in the picture) in our lab to test this product! It works with an Arcade Tankstick game controller as well (which is really not a USB game device but a keyboard/trackball on two USB ports).
KikanYes! The ones in the box (not on the shelves) are "bad apples" that are still not working. Sadly keyboard.io is one of them. We did list those on the compatibility page. Another one that isn't working is the Wooting. Those two are our top priority to make those work.