Having Trouble Centering Thumbnails In the Gallery

Greetings! I am having difficulty getting thumbnails to center within the gallery. My website is located at https://www.hkmurphyart.com. I followed the advice that I found in another post:

https://www.ads-software.com/support/topic/center-thumbs?replies=5#post-6609465

But neither the Admin CSS suggestion nor Hymer’s alternative CSS styling made any difference. I tried using the following CSS styling:

.ngg-gallery-thumbnail img { display: inline!important; }

That had no effect. I also tried:

.ngg-gallery-thumbnail img { margin-left:auto!important; margin-right:auto!important; }

That worked for Hymer, it had no effect for me. I tried something radical to see if I could apply ANY CSS rules to that class that would show up in the layout:

.ngg-gallery-thumbnail img { border-style: solid!important; border-width: 5px!important; border-color: #FF0000!important; }

…but I still see no difference, so I’m not convinced that the name is correct for my CSS class. Can you verify that I’m using the correct CSS class name to affect the thumbnail image for the theme I’m using please? Or perhaps tell me which CSS class name I should be using, if “ngg-gallery-thumbnail” isn’t correct? Please and thank you!

– Logan