Changing Thumbnail Size in Archive and Category Lists

Hi. I’d like to be able to enlarge the thumbnails on my Category lists and make them square versus circles. I found a closed topic that is exactly the same as my issue, and it was suggested to add the following to Custom CSS:

article.search-entry a.search-thumb,
article.search-entry a.search-thumb img {
border-radius: 0 !important;
height: 120px !important;
width: 120px !important;
}

I added the code with no change to the thumbnails. Any assistance would be greatly appreciated. (Couldn’t attach a screenshot for some reason, but the appearance is the same as that included in this discussion.)