First make sure in /etc/minidlna.conf
inotify=true
check /var/log/minidlna.log
may found
[2021/08/22 04:14:10] monitor.c:216: warn: WARNING: Inotify max_user_watches [8192] is low or close to the number of used watches [30] and I do not have permission to increase this limit. Please do so manually by writing a higher value into /proc/sys/fs/inotify/max_user_watches
Fix it
echo fs.inotify.max_user_watches=16384 | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
sudo systemctl restart minidlna