verify these points
-the main form must be visible to fire its childs forms-can maybe activate child forms in main form activate event (when it's visible)
-the child forms must have showWindow=1 (in the parent)
-is your main form top level ?
read this msdn link : https://msdn.microsoft.com/en-us/library/aa975765%28v=vs.71%29.aspx
-Another thing do you run an exe with a config.fpw (give details)?