This prompt is usually caused by the abnormal connection of U-Shield hardware, abnormal U-Shield driver, or failure to select or wrong certificate when the page prompts "Please select my certificate for signing".

the initial solution is that the certificate can be recognized when the Internet shield is inserted, but the signature failure occurs in the business operation, so it can be determined that the problem lies in the certificate. Check the expiration time of the certificate and find that it has not expired. Uninstall the certificate and reinstall it. Problem solved.