I heard back from Vistana, Here is their response to the email that I sent above:
Upon checking our website, I can confirm that the Do Not Show Me This Message button is currently functioning correctly. If you wish not to be advised of the Third-Party fee, you may check the box, and the pop-up message will no longer appear.
Regarding searching flexible dates, we are aware that the option is currently unavailable, and we are working diligently to rectify the issue. Currently, we do not have an estimated date as to when this option will be available again. There is currently a calendar available online that provides suggestion for alternate search dates as well.
Please feel free to contact Elite Member Services to check a range of dates. ...Please feel free to contact us again should you need any further assistance.
I checked the "Do Not Show Me" message and for the first time, it actually didn't show up! How about all of you?