The proxy server acts as an intermediate server that relays requests between a client and a server. The proxy server keeps track of all the client-server interactions and outputs a log of the entire TCP communication. This allows you to monitor exactly what is going on, without having to access the ...

As you mentioned, the connection from Apache to AEM is http. That's why AEM is using http for internal communication. Have you tried enabling SSL on AEM?

Please refer to this article and check if it fixes the issue:  

Are you getting the same error using SOAP UI? Also, have you installed the WSDL server's SSL certificate in the AEM Forms server's java keystore?

Please follow the link below to enable SSL access on dispatcher:https://experienceleague.adobe.com/docs/experience-manager-dispatcher/using/configuring/dispatcher-ssl.html?lang=en 

Please refer to these articles.https://myaemlearnings.blogspot.com/2020/07/unit-testing-hands-on-for-sling-servlet.htmlhttps://www.youtube.com/watch?v=kVdF3Q8r8ZYhttps://www.youtube.com/watch?v=hY_b3d9VZ_khttps://aem4beginner.blogspot.com/unit-testing-hands-on-for-sling-servlet 

l would request you to log a Support ticket for this, as this requires deeper investigation at your side. Thanks.

Yes, I did. I am rendering the form as HTML only. It is working as expected for me, as you can see below.  

I have done the same in this form[0]. I have used data connection in Designer to call the WSDL which adds the input A and B.  JavaScript used:form1::preSubmit:form - (JavaScript, client) validation=true; if(form1.MainForm.Fields.Body.Add.intA.isNull || form1.MainForm.Fields.Body.Add.intB.isNull) // ...

It's because there are still two issues in your form:1. You are executing the validation script in calculate event instead of Validate event of the form.2. execValidate() returns empty[0]. Why you are checking its return value as below? if ( MainForm.execValidate() == true )[0]: https://help.adobe.c...