Can not resolve Error: .MixinName is undefined on line

when I'm running my .net6.0 web project I get numerous errors about undefined mixins.

I tried many things but still can not fix this error.

Here is some more information about the project that can be useful:

• All .less file names stat with underscore "_".
• All .less files are imported to styles.less file.
• I import the file with the mixins like this: @import "../_mixins.less";
• When calling a mixins always doing like this: .mixin-name();
• In Index.cshtml file I have link with the compiled css:
• In the Statup.cs I configure the service like this:

services.AddWebOptimizer(pipe =>
{
    pipe.AddLessBundle("/css/styles.min.css", "css/**/*.less")
        .MinifyCss();
}