Error in 3.6 HELP

Ok I tried to upgrade to 3.9 but it had errors so I restored my original 3.6 code and when I run it I get this.  Please help Production store is down

Server Error in '/' Application.

Operation could destabilize the runtime.

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.Security.VerificationException: Operation could destabilize the runtime.

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:


[VerificationException: Operation could destabilize the runtime.]
   SevenSpikes.Nop.Plugins.Core.DependencyRegistrar..ctor() +12

[TargetInvocationException: Exception has been thrown by the target of an invocation.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +113
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +206
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +83
   System.Activator.CreateInstance(Type type) +11
   Nop.Core.Infrastructure.NopEngine.RegisterDependencies(NopConfig config) +452
   Nop.Core.Infrastructure.NopEngine.Initialize(NopConfig config) +20
   Nop.Core.Infrastructure.EngineContext.Initialize(Boolean forceRecreate) +92
   Nop.Web.MvcApplication.Application_Start() +30

[HttpException (0x80004005): Exception has been thrown by the target of an invocation.]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +9964625
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +118
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +172
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +339
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +296

[HttpException (0x80004005): Exception has been thrown by the target of an invocation.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9946132
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +90
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +261

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1087.0

Please Follow the upgrade procedure carefully
then restart your webserver and see if it works

You are facing problem. Someone had post for same.

Follow this

Operation could destabilize the runtime

Thanks,
Jatin