Site Sync Error after upgrading to Sitefinity 9.1

After upgrading from sitefinity 6.1 to 9.1, SiteSync is failing.  The only error message I can generate is the below.

I tried to put in a real support ticket about this, but your new support site errors out when it tries to provision an account. 

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The type 'Telerik.Sitefinity.Modules.SiteSync.Web.SiteSyncService', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: The type 'Telerik.Sitefinity.Modules.SiteSync.Web.SiteSyncService', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:

[InvalidOperationException: The type 'Telerik.Sitefinity.Modules.SiteSync.Web.SiteSyncService', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found.] System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(String constructorString, Uri[] baseAddresses) +62739 System.ServiceModel.HostingManager.CreateService(String normalizedVirtualPath, EventTraceActivity eventTraceActivity) +1429 System.ServiceModel.HostingManager.ActivateService(ServiceActivationInfo serviceActivationInfo, EventTraceActivity eventTraceActivity) +52 System.ServiceModel.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath, EventTraceActivity eventTraceActivity) +598 [ServiceActivationException: The service '/Sitefinity/Services/SiteSync/SiteSyncService.svc' cannot be activated due to an exception during compilation. The exception message is: The type 'Telerik.Sitefinity.Modules.SiteSync.Web.SiteSyncService', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found..] System.Runtime.AsyncResult.End(IAsyncResult result) +486572 System.ServiceModel.Activation.HostedHttpRequestAsyncResult.End(IAsyncResult result) +174 System.ServiceModel.Activation.ServiceHttpHandler.EndProcessRequest(IAsyncResult result) +6 System.Web.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar) +129

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34280

Hi Robert, can you please check two things:

1) Those libraries Telerik.Sitefinity.SiteSync.dll and Telerik.Sitefinity.SiteSync.Impl.dll exist in your bin folder. 

2) Site Sync module installed in the backend.

If both of them is true, please try to uninstall and install site sync module. create backup first

Hi Victor - thanks for the quick reply.

Both dlls are in my bin folder.

For #2 - I am guessing you mean the under Modules & Services the Module is active.  If so, yes it is marked as Active.

- I see the option for uninstalling the module, but how to i re-install it?  sorry I have not gone through that process.

Dlls exists in source and destination server?

Reinstall - i mean uninstall and install it again. After installation you need to configure sitesync again.

Victor - thanks for your help,   re-installing the module actually didn't fix our problem  We had an issue in our source files where not all the proper files were added to the project. You suggestion about the dlls made me go back and double check that - and that lead to the discovery.