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Because the information we have is limited, we recommend that you first do the following checks:
1, Check if there are any error messages when the Short Date Picker doesn't work.
2, Whether the short date picker was created using custom code? If yes, ensure that the custom code used for the Short Date Picker is up-to-date and compatible with the current SharePoint Online environment.
3, Please provide more details about this issue so that we can resolve it better.
Thank you.
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