1, if you use the FTP that comes with windows, check Write in the home directory tab.
2. If you use third-party software (such as ServerU), tick Create in the user's directory access rights.
You said that the external network can be downloaded, but you can't create a directory, right? Have you built FTP with third-party tools?
If the server's disk is in NTFS format, you can uncheck Enable Quotation Management on the Quotation tab.