Tag cloud won't "cloud"

I am using atahualpa 3.6.4 and although I have the tag cloud widget in the right place, and it shows up in the sidebar, it won't make a nice "cloud". It just shows up as black text.
URL is declutteringhelp.com
I have another blog which uses version 3.4.6 and the tag cloud works fine.
In your reply, please use plain english. I have read other posts about tag clouds but frankly could not understand the advice - not very technical.

thanks in advance.