Withelist folder not working

hi to all, we have to monitoring one folder (this folder was a mount point for nfs)
if i set the whitelist_external_dir and the folder_watcher in config i receive this error:

not a directory @ data['whitelist_external_dirs'][0]
Invalid config for [folder_watcher]: not a directory for dictionary value @ data['folder_watcher'][0]['folder']. Got '/tmp/tvcc'. (See /config/configuration.yaml, line 24).

my HA are:

arch armv7l
dev false
docker true
hassio true
os_name Linux
os_version 4.19.97-v7l+
python_version 3.7.7
timezone Europe/Rome
version 0.108.5
virtualenv false

Lovelace

dashboards 1
mode storage
resources 9
views 15

can you have an idea to have sensor on that folder??

thanks