Redmine

I created a custom theme in themes/ass and added these:
/var/www/redmine/themes/ass$ tree
.
├── favicon
│   └── Abellard Favicon.png
├── images
│   └── abellardSS.png
└── stylesheets
├── application.css

In application.css I have (based on example in https://www.redmine.org/projects/redmine/wiki/Themes and then https://www.redmine.org/projects/redmine/wiki/HowTo_create_a_custom_Redmine_theme:

/* load the default Redmine stylesheet */
/* @import url(../../../app/assets/stylesheets/application.css); */

/* add a logo in the header */
#header {
    background: #507AAA url(../images/abellardSS.png) no-repeat 2px;
    padding-left: 86px;
}

/* move the project menu to the right */
#main-menu { 
    left: auto;
    right: 0px;
}

I restarted Apache for good measure, but I apply the theme, I get a page that clearly doesn't load the css.

I guess there are some more changes to Redmine 6 that effect this? Why would my page not load correctly?