Configuring External Storage: Dir can' t open

snap
#1

On the Ubuntu 18.04 installed snap, then installed nextcloud. The Nextcloud works well. I used External Storage, and used Local(https://docs.nextcloud.com/server/15/admin_manual/configuration_files/external_storage/local.html), but when I opened it, log error: opendir(/home/duoker/ntfs/data/): failed to open dir: Permission denied at /snap/nextcloud/13453/htdocs/lib/private/Files/Storage/Local.php#125
How can I do?