I get this error The playback failed to find the control with the given search properties

public HtmlButton UILoginButton
        {
            get
            {
                if ((this.mUILoginButton == null))
                {
                    this.mUILoginButton = new HtmlButton(this);
                    #region Search Criteria
                   this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.Id] = null;
                   this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.Name] = null;
                    this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.DisplayText] = "Login";
                    this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.Type] = "button";
                  this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.Title] = null;
                    this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.Class] = "btn btn-primary px-4";
                    this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.ControlDefinition] = "class=\"btn btn-primary px-4\" type=\"button;
                    this.mUILoginButton.SearchProperties[HtmlButton.PropertyNames.TagInstance] = "1";
                    this.mUILoginButton.WindowTitles.Add("http://localhost:81/etesplus/#/security/login");
                    #endregion
                }
                return this.mUILoginButton;
            }
        }