Linux Desktop App Not Seeing Fonts [Raspberry Pi]

I am unable to use fonts which are installed on the Raspberry Pi system. I have tried to change the font of a Label using Me.FontName = "FreeMono Regular" and Me.FontName = "FreeMono.ttf" but the font is not used.

I ave also tried the function from this page to check if a font is available

Function FontAvailable(FontName As String) As Boolean
  Var i As Integer
  For i = 0 To System.FontCount - 1
    If System.FontAt(i) = FontName Then
      Return True
    End If

  Return False
End Function

The above function works on Mac but not on Raspberry Pi.