Excel VSTO add-ins being blocked from starting

Brett Holmes 21 Reputation points
2020-06-19T03:06:15.32+00:00

HI,

For some reason this won't post unless I add tags, and the tags that come up aren't really related - so apologies for posing in the wrong area!

I have a number of VSTO add-ins that will no longer load after a recent update due to a ClickOnceAddInTrustEvaluator error. This is new as of the recent update which installed this morning.

I don't have a proper security certificate and don't have any desire to purchase one as the add-ins are only used by me, but it won't even run off a Test Certificate in debug mode.

Error message as follows:

************** Exception Text **************
System.Security.SecurityException: Customized functionality in this application will not work because the certificate used to sign the deployment manifest for <snip> or its location is not trusted. Contact your administrator for further assistance.
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInTrustEvaluator.VerifyTrustPromptKeyInternal(ClickOnceTrustPromptKeyValue promptKeyValue, DeploymentSignatureInformation signatureInformation, String productName, TrustStatus status)
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInTrustEvaluator.VerifyTrustUsingPromptKey(Uri manifest, DeploymentSignatureInformation signatureInformation, String productName, TrustStatus status)
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.ProcessSHA2Manifest(ActivationContext context, DeploymentSignatureInformation signatureInformation, PermissionSet permissionsRequested, Uri manifest, ManifestSignatureInformationCollection signatures, AddInInstallationStatus installState, TrustStatus sha256TrustStatus, X509Certificate2 sha256PublisherCert)
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.VerifySecurity(ActivationContext context, Uri manifest, AddInInstallationStatus installState)
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.InstallAddIn()
The Zone of the assembly that failed was:
MyComputer

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Accepted answer
  1. Anonymous
    2020-06-19T03:21:37.9+00:00

    Excel and VSTO are not currently supported here on QnA. They're actively answering question in dedicated forums here.

    https://social.msdn.microsoft.com/Forums/Lync/en-US/home?forum=exceldev

    https://social.msdn.microsoft.com/Forums/vstudio/en-US/home?forum=vsto

    --please don't forget to Accept as answer if the reply is helpful--


    Regards, Dave Patrick ....
    Microsoft Certified Professional
    Microsoft MVP [Windows Server] Datacenter Management

    Disclaimer: This posting is provided "AS IS" with no warranties or guarantees, and confers no rights.

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  1. Brett Holmes 21 Reputation points
    2020-06-19T03:47:49.81+00:00

    Thanks. Reposted in the correct location.

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