An existing connection was forcibly closed by the remote host

Solution 1:

This generally means that the remote side closed the connection (usually by sending a TCP/IP RST packet). If you're working with a third-party application, the likely causes are:

• You are sending malformed data to the application (which could include sending an HTTPS request to an HTTP server)
• The network link between the client and server is going down for some reason
• You have triggered a bug in the third-party application that caused it to crash
• The third-party application has exhausted system resources

It's likely that the first case is what's happening.

You can fire up Wireshark to see exactly what is happening on the wire to narrow down the problem.

Without more specific information, it's unlikely that anyone here can really help you much.

Solution 2:

Using TLS 1.2 solved this error.
You can force your application using TLS 1.2 with this (make sure to execute it before calling your service):

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 

Another solution :
Enable strong cryptography in your local machine or server in order to use TLS1.2 because by default it is disabled so only TLS1.0 is used.
To enable strong cryptography , execute these commande in PowerShell with admin privileges :

Set-ItemProperty -Path 'HKLM:\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type DWord
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type DWord 

You need to reboot your computer for these changes to take effect.