Could not load file or assembly

[Kingfisher Direct]

Trying to test the API which was working on 2020 R1 but since upgrading to 2023 R2 I am now getting the below error. Do you have any suggestions how I fix this error?

 

[FileNotFoundException: Could not load file or assembly 'MvvmHelpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.]
   System.Signature.GetSignature(Void* pCorSig, Int32 cCorSig, RuntimeFieldHandleInternal fieldHandle, IRuntimeMethodInfo methodHandle, RuntimeType declaringType) +0
   System.Reflection.RuntimeMethodInfo.get_ReturnType() +44
   System.Web.Http.Controllers.ReflectedHttpActionDescriptor.GetReturnType(MethodInfo methodInfo) +15
   System.Web.Http.Controllers.ReflectedHttpActionDescriptor.InitializeProperties(MethodInfo methodInfo) +28
   System.Web.Http.Controllers.ReflectedHttpActionDescriptor..ctor(HttpControllerDescriptor controllerDescriptor, MethodInfo methodInfo) +41
   System.Web.Http.Controllers.ActionSelectorCacheItem..ctor(HttpControllerDescriptor controllerDescriptor) +214
   System.Web.Http.Controllers.ApiControllerActionSelector.GetInternalSelector(HttpControllerDescriptor controllerDescriptor) +175
   System.Web.Http.Controllers.ApiControllerActionSelector.GetActionMapping(HttpControllerDescriptor controllerDescriptor) +13
   System.Web.Http.Routing.AttributeRoutingMapper.AddRouteEntries(SubRouteCollection collector, HttpConfiguration configuration, IInlineConstraintResolver constraintResolver, IDirectRouteProvider directRouteProvider) +129
   System.Web.Http.Routing.<>c__DisplayClass4.<MapAttributeRoutes>b__1() +57
   System.Web.Http.Routing.RouteCollectionRoute.EnsureInitialized(Func`1 initializer) +52
   System.Web.Http.Routing.<>c__DisplayClass2.<MapAttributeRoutes>b__0(HttpConfiguration config) +91
   System.Web.Http.HttpConfiguration.EnsureInitialized() +23
   System.Web.Http.GlobalConfiguration.Configure(Action`1 configurationCallback) +43
   WebAPI.WebApiApplication.Application_Start() +43