This problem could be caused because of ViewState() property of either page or control, please check if webforms ViewState() is disable or control's ViewState() could be disabled , if any of these ViewState Propperty is disabled, this problem could occur, so please enable ViewState of both Page and control, it can solve your issue.
void Page_Load(object sender, System.EventArgs e)
// Set EnableViewState to false to disable saving of view state
myControl.EnableViewState = false;
display.Enabled = false;