Help! cannot receive request from java spring framework

Hello,
I'm using CentOS Web Panel on CentOS 7 and currently I have this problem.
My server is intended to receive a push data in XML format from 3rd party using java spring, and it return with 403 forbidden access error. While trying to find solution from the internet, it suggested that we need to disable mod_security. When I did this, the 403 is no longer occurred, however they don't receive any responses from the server now. Please note that the connection is ok, and they can push data using curl from terminal. The problem exist when they pushed data from java spring.
How we can solve this issue? Do we need to install something in cwp related to this java spring framework?
(Note. previously I used my dedicated server running in CentOS7 but with cPanel, and it worked properly)

Thanks,
Wahyu

Are you whitelisted in the CSF firewall? Temporarily disable & test...

Hello,

I have whitelisted the incoming IP and test the connection. It was perfectly fine.
The 3rd party even can curl using terminal to call our API
However, when they use java spring, our server give no response to them
Just wondering, what setting is needed to make the 3rd party can push using java spring?

Thank you