The TabControl will not create the controls on a TabPage until that TabPage is actually selected. For instance, if you have a TabControl with two TabPages then, when it is first displayed, only the controls on the first TabPage are actually created until you select the second TabPage. Perhaps what you're doing is confusing that mechanism somehow.

You could try making the second TabPage the selected tab to begin with and then select the first one when your Panel becomes visible. That might force the creation of the controls on the first page. It's a workaround but it may be necessary.