Description

Horizon might fail to start due to the fact that Sitecore.Horizon.Editor.Integration.config contains a reference to a missing type:

<signingProvider type="sitecore.services.infrastructure.sitecore.security.symetrickeysigningprovider, sitecore.services.infrastructure.sitecore">

Solution

To resolve the issue:

1. Open the [your_website]\App_Config\Modules\Horizon\Editor\Sitecore.Horizon.Editor.Integration.config file.
2. Find the following code:

   <signingProvider type="sitecore.services.infrastructure.sitecore.security.symetrickeysigningprovider, sitecore.services.infrastructure.sitecore">

   and replace with

   <signingProvider type="Sitecore.Services.Infrastructure.Security.SymmetricKeySigningProvider, Sitecore.Services.Infrastructure">