The deployment identity at the deployment provider is not the same as the original deployment identity

Problem

I usually get this error whenever I tried to publish a click once app with a different target architecture then what is currently installed on a machine (x86 vs x64)

OR

When the signature/certificate of the application is different than the original publish

Solution

I would try making sure that your target architecture has not been changed (if you published it originally as x32, make sure the version you are trying to install is still x32)

or

make sure that nothing has changed with the signature settings (if you published originally with a certificate, make sure it is still the same certificate)

If you made these changes on purpose however, all you'll need to do on the host machine is uninstall the existing application on the machine, and re-install with the version you are trying to install, that should resolve the error and allow you to install the new version.

I just ran into this error message in the following situation. I updated my ClickOnce application to sign the ClickOnce manifests with a trusted certificate issued by my organization. This particular application was using a self-signed certificate in the previous version. This in turn changes the publisherIdentity element (https://msdn.microsoft.com/en-us/library/dd996956.aspx) and it's generated hash in the ClickOnce Deployment Manifest (.application file).

In your situation, it's possible that the previous developer re-signed the application with a different certificate than the previous version. Or perhaps the application had not been signed in the previous version. Judging by the error message you are seeing, this is almost certainly an application that has been published as a ClickOnce application.

Assuming that you have your hands on the code, and that you are using Visual Studio, right-click on the project in Solution Explorer and select Properties. Then click on Signing to see signing details such as whether or not the manifests are signed, and if so, which certificate was used.

You will get the same exception when you changed the "Publish Location" -> "Installation Folder URL (if different than above)", but forgot to change the following: "Install Mode and Settings" -> "Updates..." -> "Update location (if different than publish location)".