What is TEdit.Caption?
Why is there a Catpion for the TEdit and why are you using that.
For the content of a TEdit you should use TEdit.Text (not Caption).
TEdit doesn't have a caption (which I assume could be confused with a connected label).
TEdit.CopyToClipBoard is implemented like this:
if (ACustomEdit.EchoMode = emNormal) and (ACustomEdit.SelLength > 0) then
Clipboard.AsText := ACustomEdit.SelText;
So it actually only copies selected text. I'm not sure why.
So either do Edit1.SelectAll directly in front of Edit1.CopyToClipBoard or folow the suggestion of dseligo.
(Ah, Ally beat me to it

)