I've got the tractorcow/silverstripe-imagegallery module installed on a website I'm building with SS3.1, only problem is when I look at the gallery pages they're not linking in the CSS files for the module (so all of the gallery data is displaying as unstyled) and the gallery_ui popup things aren't working (so when you click on an image thumbnail it just opens up the image in a blank window ... which seems as if it might also be an issue with the CSS file not being linked into the page as well as the JS).
No error messages or anything, the site just seems to be ignoring those CSS files
I can't for the life of me figure out why, everything looks like it's as it should be ... but it's been a while since I've used silverstripe and it's all changed, so maybe I'm not even looking in the right place ...
Can anyone please help or point me in the right direction?

try replacing

Requirements::themedCSS('ImageGallery');

with

Requirements::css( 'ImageGallery/css/ImageGallery.css', 'screen,projection' );

in ImageGallery / code / ImageGalleryPage.php

Thanks for the reply.
Changing that line didn't work though.

it does work, though there are some minor problem with css.

I have tested in localhost.

Please check the module name is ImageGallery. If not try with module as below

Requirements::css( ' - module name - /css/ImageGallery.css', 'screen,projection' );

Oh, right! I don't know how I missed that .... changed it to:
Requirements::css( ' ImageGallery-3.1/css/ImageGallery.css', 'screen,projection' );
And that seems to have for worked kinda .. though now it's not loading the images in the galleries, just show the loading gif

try disable css in ImageGallery/css/ImageGallery.css

.gallery-layout {
/* background: url("../images/ajax-loader-lg.gif") no-repeat scroll center center transparent; */
}

.gallery-layout li a {
/* visibility: hidden; */
}