Fix: An Unexpected Error is Keeping You from Copying the File 0x800700DE - Microsoft Windows
If you are trying to copy a file with a complex or too long of a name over the network in Microsoft Windows, you will receive an error message related below.
An unexpected error is keeping you from copying the file. If you continue to receive this error, you can use the error code to search for help with this problem. Error 0x800700DE: The file type being saved or retrieved has been blocked.
Make sure you aren’t exceeding a max file length of 128 Characters or using any complex characters if you are trying to copy a file to a Microsoft SharePoint network location.