Fluent UI Blazor component FluentDatePicker does not open its calendar

I'm new to blazor and to the fluent ui library for blazor. I think they are both awesome.Now I have this problem with the FluentDatePicker control in my blazor server application. It just does not open its calendar when I click the icon on the right side of the control.

I read on a similar question here that maybe it has something to do with css styles, and the solutions was to add the line:

<link href="{PROJECT_NAME}.styles.css" rel="stylesheet" />

to the _Host.cshtm file.

Now I'm using net version 8 and I suppose the file is now App.razor and it already has the line, as I used the blazor fluent ui template from visual studio to create my blazor server application.

I have been looking for a file like contab_blazor2.styles.css and can't find one.Where is that file? And has another developer experienced this kind of problem and maybe has a solution for it?

Thanks ...