@Tilen-Štraus Glad you got it working, and thank you for sharing your solution for others who may run into the same trouble 😄
Popular Tags Widget
Here is another widget, this one displays the popular tags in your forum. You can set how many tags to display in the widgets ACP.
Nice, How about a 3D tag cloud plugin?
(click on Create Sphere 3D)
Both suitable for different niches. Though I love second one, I will be choosing first as it is more suitable in my kind of forum.