<t>This is caused by the "ClickOnce Trust Prompt Behavior": https://msdn.microsoft.com/en-us/library/ee308453.aspx<br/>
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To adjust this, simply change the values in the Registry and you should be able to install the application.<br/>
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To enable the ClickOnce trust prompt by using the registry editor Open<br/>
the registry editor:<br/>
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Click Start, and then click Run.<br/>
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In the Open box, type regedit, and then click OK.<br/>
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Find the following registry key:<br/>
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\HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT.NETFramework\Security\TrustManager\PromptingLevel<br/>
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If the key does not exist, create it.<br/>
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Add the following subkeys as String Value, if they do not already<br/>
exist, with the associated values shown in the following table.<br/>
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On my computer, the values were set to "Disabled" and I have no clue which application did that. I changed the values to default and now everything works again like it should.<br/>
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Or you can just delete the key "TrustManager" itself and everything is working as well.</t>
