for the benefit of
@cindi and
@Ralph Sir Edward and others unfamiliar with Marriott's res system, I'd like to share what I did to make about 80 successful and consecutive reservations with Marriott over the past 12 years. I go to the marriottvacationclub.com site and find the Helpful tools section and find the clickable "when can I reserve". Marriott releases a week of inventory about 1 year in advance. They release all of the week's inventory on a single day. So, for example, if I wanted to book Thursday June 2, 2022 or Sunday June 5, etc., I plug in those dates and Marriott tells me that if I'm reserving on a 12 month basis, I need to book either of these dates on Thursday, June 2, 2011. If I'm on a 13 month basis (multiple weeks) I should book on Monday May 3, 2021. The phones and internet are activated at 9 am Florida time.
With my non-Marriott weeks (Sands of Kahana) it is similar but not exactly the same. I book exactly 365 days in advance on a rolling basis.
So, I will set the alarm clock (I'm 3 time zones from Florida), and either be on the phone or internet when the first open. It has worked every single time for me. Yes, I have a "season" (red and white) but they don't open an entire season at once. It is done a year in advance on a week by week basis or on a 365 day basis (depends on which of my timeshares I'm reserving). For high demand weeks (like Thanksgiving in Palm Desert) it is necessary to do this. The OP and Ralph didn't do this and it is understandable why they had a problem.
And yes, Marriott will give you a replacement week. It shows up in your ii account just like you made the deposit and you can use it to exchange. Mine were good for about a year and traded fairly well.
Cindi, I'm interpreting your "special week" as being weeks 51 and 52. At week 51 of last year (2020), the owners of those weeks reserved them. Perhaps within a few hours of becoming available, all were probably snatched up. That is why you are having a problem. Contact Marriott and work with them to get a replacement week. You likely won't be able to exchange back into weeks 51 or 52, but should be able to find something, somewhere to exchange into.