Hello.I suppose this is for a customer of yours.Unfortunately, the most important information is completely missing from the report: The steps made, and the behavior observed.What is needed are the actual symptoms and error messages, and the certificates (public part only) which were, in customer's view, not generated as they should.In earlier versions of QuickOPC (I believe including 5.63), the default certificate validity was 50 years when targeting .NET Framework, or 1 year when targeting .NET 6+. In newer versions (since 2023.1: kb.opclabs.com/What%27s_new_in_QuickOPC_2023.1 ), it is 5 years, regardless of the .NET runtime targeted.To your questions:

• What could cause a client certificate to be generated with a ~1-year expiration instead of the expected long-term validity?

In version 5.63, this should only happen when targeting .NET 6+. I have doubts that this happening. Will need to see the certificate.

• What could lead to intermittent certificate errors at startup even when the certificate is not expired?

There is no way to answer this without having the error details.

• Why would deleting and regenerating the certificate temporarily resolve the issue?

Cannot answer because the error details are missing.

• Whether this behavior is known in version 5.63.246 or related to certificate handling, storage, or trust validation timing

It is not known behavior. 

Best regards

Hi team,I’m looking for some guidance on an issue involving OPCLabs.QuickOPC / OPC Data Client using the QuickOPC 5.63 NuGet package (specifically version 5.63.246).The behavior being observed is related to client certificates. Initially, it appeared that certificates were expiring after about one year, even though the expectation is that auto-generated client certificates should have a much longer validity period (around 49 years). There were no major system or application changes around the time this started happening.More recently, it has become clear that the issue is not limited to expiration. There are also intermittent certificate-related errors occurring during application startup, even when the certificate is still valid.A temporary workaround has been identified: deleting the client certificate and restarting the application causes a new certificate to be generated, which resolves the issue for a period of time. However, the problem eventually returns, typically after subsequent restarts.Based on documentation and prior understanding, the OPC Data Client should:

• Automatically generate a UA client certificate on first run
• Store it under
  Code:

  %CommonApplicationData%\OPC Foundation\CertificateStores\UA Applications
• Use a long validity period (approximately 49 years)

Given that, I’m trying to understand:

• What could cause a client certificate to be generated with a ~1-year expiration instead of the expected long-term validity?
• What could lead to intermittent certificate errors at startup even when the certificate is not expired?
• Why would deleting and regenerating the certificate temporarily resolve the issue?
• Whether this behavior is known in version 5.63.246 or related to certificate handling, storage, or trust validation timing

Any insight into potential causes or recommended approaches for diagnosing this would be greatly appreciated!

Let me know if there is any additional information or logging that would be useful!