DataSource.Error: The underlying connection was closed

Hi JoergSch ,

Here are the main causes of the “Could not establish trust relationship for the SSL/TLS Secure Channel with Authority” message:

• Self-signed certificates: These certificates are often generated for free. However, they don’t provide as much trust as commercial certificates.
• Expired certificates: Most SSL certificates are only valid for a year. Therefore, you’ll need to renew your certificate as it nears its expiration date.
• Certificates not signed by a trusted Certificate Authority (CA): Like self-signed certificates, a lesser-known certificate provider might not be trusted by every browser.
• Free SSL certificates: There are a few free CAs, but sometimes their root certificates must be manually imported into your browser to clear the error.
• Certificates that are missing a chain/intermediate certificate: Most trusted certificates ask you to install at least one other chain/intermediate certificate to link your SSL certificate to a trusted source. However, this process depends on the browser you use. For example, Internet Explorer can automatically download intermediate certificates, but Mozilla Firefox can’t.

About more details, you may refer to

How To Fix the “Could Not Establish Trust Relationship for the SSL/TLS Secure Channel with Authority” Error (kinsta.com)

Best Regards,

Stephen Tao

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