Hi there!
The reason for the error is pretty clear, but checking shows that no such property has been assigned to the file if we search for this property.
I uploaded a lot of files using this method, and for the first time I got stuck on one such file.
https://api.dropboxapi.com/2/files/get_metadata


https://api.dropboxapi.com/2/file_properties/properties/search


https://api.dropboxapi.com/2/file_properties/properties/add


Is there something I don't see and don't understand, or is the API returning the wrong thing?