Wrong start and end date of my Flexi Passes

I purchased 3 Flexi German mobile rail passes 7 days within 1 month on December 9th 2023. I plan to travel starting on March 30th 2024. But on my order confirmation and app shows “Activate this pass by February 1 2024”. I tried to make seat reservation for March 30th, the web page shows my pass is not valid on this date. I am not able to travel with theses passes if the condition is like this. I did not recall I need to enter start and end sate during booking process. The website shows the pass can be used within 11 months from purchased date. Submitted support request but have not heard from the customer service. Anyone knows why this happens? Is there any way I can change this? The passes haven’t being activated yet. Thanks for helping!