External script Permission denied

[bala384]

Hi.. i create vnstat external script in zabbix. i follow this link (http://www.perehospital.cat/blog/how...th-with-zabbix) whats my problem my script working ubuntu users but not working root and centos users the same script. showing this error > Received value [sh: /root/zabbix_total_month_bandwidth.sh: Permission denied] is not suitable for value type [Numeric (float)]

Any One Please Help Me...