Object reference is not set to an instance of an object (+ maybe jdk version problem?)

Hello, I'd like to ask a question about the object reference error.

I called the service, but the following error occurred.

(The following error occurs when calling the SOAP service created by SOAP UI.)

'''Object reference is not set to an instance of an object.'''

According to the person who created the service, he always succeeded when calling in his environment.

There's a problem when calling the service from outside.

It wasn't about the firewall.

And additionally, the error message came back because the Unicode was broken.

I think the SOAP UI setting was wrong in the first place, but they said no.

It does not fail unconditionally, but calls are successful when approaching a different version of the solution.

Is there a case like this sometimes?

Leave a question because I can't figure out the answer.

I want to see the error code, but I can't find the detailed error because I'm calling.

I don't know anything but the error.

Can such an error occur if the Java version or HTTP version of the solution calling the service is different?

I'm sorry it's such an abstract question.