Hi

We are currently using DNN 5.6.0 in Production and we are planning to upgrade latest DNN version.

For that I am planning follow the upgrade path as

5.6.0 -> 5.6.8 -> 6.2.8 -> 7.3.2 and so on.

I am able upgrade from 5.6.0 to 5.6.8 successfully.

after updating 6.2.8 I am getting an below error & need your assistance to fix this issue please.

[MissingMethodException: Method not found: 'System.Collections.Generic.List`1<DotNetNuke.UI.Skins.EventListeners.SkinEventListener> DotNetNuke.Application.DotNetNukeContext.get_SkinEventListeners()'.]
DotNetNuke.Professional.HttpModules.LicenseValidatorModule.Init(HttpApplication application) +0
System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +480
System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +336
System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +350
System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +382

[HttpException (0x80004005): Method not found: 'System.Collections.Generic.List`1<DotNetNuke.UI.Skins.EventListeners.SkinEventListener> DotNetNuke.Application.DotNetNukeContext.get_SkinEventListeners()'.]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +11420374
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +88
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +4405156