proxmox backup error

INFO: starting new backup job: vzdump 104 --compress zstd --remove 0 --storage NFS-QNAP-Proxmox-Backup --mode snapshot --node pve --notes-template '{{guestname}}'
INFO: Starting Backup of VM 104 (lxc)
INFO: Backup started at 2023-06-27 09:08:40
INFO: status = running
INFO: CT Name: uptimekuma
INFO: including mount point rootfs ('/') in backup
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: create storage snapshot 'vzdump'
Logical volume "snap_vm-104-disk-0_vzdump" created.
INFO: creating vzdump archive '/mnt/pve/NFS-QNAP-Proxmox-Backup/dump/vzdump-lxc-104-2023_06_27-09_08_40.tar.zst'
INFO: tar: /mnt/pve/NFS-QNAP-Proxmox-Backup/dump/vzdump-lxc-104-2023_06_27-09_08_40.tmp: Cannot open: Permission denied
INFO: tar: Error is not recoverable: exiting now
INFO: cleanup temporary 'vzdump' snapshot
Logical volume "snap_vm-104-disk-0_vzdump" successfully removed
ERROR: Backup of VM 104 failed - command 'set -o pipefail && lxc-usernsexec -m u:0:100000:65536 -m g:0:100000:65536 -- tar cpf - --totals --one-file-system -p --sparse --numeric-owner --acls --xattrs '--xattrs-include=user.*' '--xattrs-include=security.capability' '--warning=no-file-ignored' '--warning=no-xattr-write' --one-file-system '--warning=no-file-ignored' '--directory=/mnt/pve/NFS-QNAP-Proxmox-Backup/dump/vzdump-lxc-104-2023_06_27-09_08_40.tmp' ./etc/vzdump/pct.conf ./etc/vzdump/pct.fw '--directory=/mnt/vzsnap0' --no-anchored '--exclude=lost+found' --anchored '--exclude=./tmp/?*' '--exclude=./var/tmp/?*' '--exclude=./var/run/?*.pid' ./ | zstd --rsyncable '--threads=1' >/mnt/pve/NFS-QNAP-Proxmox-Backup/dump/vzdump-lxc-104-2023_06_27-09_08_40.tar.dat' failed: exit code 2
INFO: Failed at 2023-06-27 09:08:41
INFO: Backup job finished with errors
TASK ERROR: job errors