Hello,
Give below a try and see if it helps:
1. Access http://<ip address of tftp>:6970/ConfigFileCacheList.txt in internet browser to see all files available in TFTP server.
2. Replace ConfigFileCacheList.txt file with phone configuration file name (retrieved in above step) and access it in browser. You get a prompt to save the file.
http://<ip address of tftp>:6970/<phone config file name>