You have most likely done something wrong, I have no problems running this addon with XF2.2.
From the Addons FAQ
Q. The widget block is showing, but none of the contents of my discord server are appearing. A. This could be due to a couple of things. Number one: make sure your server ID is correct. If it's not correct, the add-on can't retrieve data from Discord. Number two: make sure the "Enable Widget" in your discord server's settings is checked. Here's how to do that: