When we send the request, we get an error, "The underlying connection was closed: Unexpected error during transmission."
Could you tell me, what the problem is?
The issue is related to the TLS 1.0 and 1.1 deprecation (08.03.2020) which resulted in getting the above-mentioned error. Currently, we have switched to TLS 1.2 version which is a more secure one and terminated the support of 1.0 and 1.1 versions. In view of this, an update to TLS 1.2 version should be performed.
Additionally, here is a couple of articles that may be helpful in the process of TLS update: