Not able to receive response during Decryption of invoice in Json format

Dear All,

We're using NAV 2016 and we're handling an e-invoicing process and during the API request and response exactly during the decryption process of sales invoice I'm receiving the follow error:

A call to System.Net.HttpWebRequest.GetResponse failed with this message: The remote server returned an error: (500) Internal Server Error.

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OK

This issue started from last week of Jan till then everything was running fine.

My troubleshoot-
1. Checked in PostMan API - it is passing through all the request and responses steps without any issues and generated proper response as expected.
2. Verified the response of previous step of decryption and the request it is passing during decryption in NAV. This looks good.
3. Code is not altered recently.
4. TLS is updated with TLS1.2 in protocols.

So, I'm suspecting this is not more of a NAV code issue since it was working fine before but something different related to security and infrastructure but not sure what exactly..

Is there a way I can catch the exact error of response instead of internal server 500 error? or any other suggestions if you've faced such situation. Please let me know.