Welcome to the Google Chat Help Community..
If you're experiencing a partial data export issue via Google Takeout, where chats after March 13, 2025 are missing. This may be a temporary issue or due to delays in data availability from Google's side. You are not alone some users have reported similar gaps. There is no official confirmation yet on a fix.
You can try again after a few days
or report this to Google directly via the Feedback
Hope it helps..