The updates I made based on a friend's answer worked. I wish he hadn't deleted the answer. I would consider it valid. Unfortunately, someone gave -1 point and he deleted the answer.

I change it: IIS -> Application Pools -> Advanced Settings

Identity = NetworkService

and I add code base:

System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;

my problem is solved.