Unable to launch userform from button on worksheet

Hey guys,

Trying to launch a form from a button on a worksheet but unable to do it, I already have the userform setup where it automatically launches when i open a workbook, however if the userform is closed the users have to then launch it though the developer tab which a lot of them dont know how..So i decided to put a button on the wrksheet to launch it but it does not launch, get a debug error...

this workbook has a code

Private Sub Workbook_Open()
UserForm1.Show
End Sub


And in my main user for i have this code

Private Sub UserForm_Initialize()
With Sheets("Database").Range("A3", Cells(Rows.Count, "A").End(xlUp))
partner = Application.Transpose(.Value2)
End With

Me.ComboBox1.List = partner

End Sub

Help