User control (referenced from another project) does not show

Hi
I have solutions with multiple projects. One of these projects is a webapplication and in this project I try to add a user control for another project. I have this line in the top of my file
  <%@ Register Assembly="UserControls" Namespace="UserControls" TagPrefix="uc1" %>
  And further down
  <uc1:TestControl ID="TestControl1" runat="server" />
I get no errors when I run the projet but the content of my user control does not show on the page.
But when I put a breakpoint in the code behind the user control it stops there.

I have tried added another user control from within the same project and that works fine.
Anybody know why this control won´t show ?

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