Dell s4112f-on Zero touch deployment failed to recieve dhcp calback

Hi,

I'm trying to setup Zero touch deployment on the Dell s4112f-on. I am following the procedure on this document on pages 39 to 41 and setting up the dhcp server on cent os 7 https://downloads.dell.com/manuals/common/os10_enterprise-ug_en-us.pdf. The DHCP process is going up to the ack stage. After this however ZTD on the switch appears to be waiting for a callback after the ack packet so it is not going to the stage where it is trying to retrieve files. I have a webserver on apache which can be accessed locally. I have attached screenshots of tcpdump running on the interface and /var/log/messages. I've also added pictures of the dhcpd conf and scripts ztd is supposed to run on the machine. I have not included a fixed address in the dhcpd.conf file as it was telling me not to do that in /var/log/messages in the past. 

On the ztd.sh script I am not trying to install the OS image again if possible I am only trying to reload the switch to a known point and automate the config using ansible. I have not included the ansible playbook but it runs as expected.

Any help would be appreciated.

Links to screenshots:

http://www.filedropper.com/screenshotfrom2019-06-0610-03-29

http://www.filedropper.com/screenshotfrom2019-06-0610-30-39

Thanks