Rescan files
On this page 2 sections
Here is the command for re-scanning files.
Sometimes you need to force Nextcloud to rescan files that have been changed by an external program etc.
This will scan all files again.
sudo docker exec -it --user www-data nextcloud-app php /var/www/html/occ files:scan --all
Here is the command for scanning a specific folder.
change "--path=" to the path you want to scan
sudo docker exec -it --user www-data nextcloud-app php /var/www/html/occ files:scan --path=/Fullmetal/files/