Are you unable to write to it locally or from another computer?
If it's from another computer, check the directory permissions. They may not align with the Samba configuration. If you want everyone (that is, "owner," "group," "everyone") to be able to write to it, they should look like this:
lrwxrwxrwx 1 [owner] [group] 17 Aug 13 12:48 /path/to/some/directory