Did you copy the EPiServer.Business.Commerce.Payment.DIBS.dll to your front-end bin folder as well?

Yes, I have a copy of the file in that folder as well.

<p>This is the full exception and stacktrace.</p> <h2></h2> <h2>Specified payment method class "EPiServer.Business.Commerce.Payment.DIBS.DIBSPaymentGateway, EPiServer.Business.Commerce" can not be created.</h2> <p><span></span><span></span>Description:<span>&nbsp;</span>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.<span>&nbsp;</span><br /><br />Exception Details:<span>&nbsp;</span>System.TypeLoadException: Specified payment method class "EPiServer.Business.Commerce.Payment.DIBS.DIBSPaymentGateway, EPiServer.Business.Commerce" can not be created.<br /><br />Source Error:<span>&nbsp;</span><br /><br /></p> <table> <tbody> <tr> <td> <pre>Line 120: try Line 121: { Line 122: cart.ProcessPayments(_paymentProcessor, _orderGroupCalculator); Line 123: Line 124: var processedPayments = cart.GetFirstForm().Payments.Where(x =&gt; x.Status.Equals(PaymentStatus.Processed.ToString()));</pre> </td> </tr> </tbody> </table> <p><br />Source File:<span>&nbsp;...</span>\Features\Checkout\Services\CheckoutService.cs<span>&nbsp;</span>&nbsp;&nbsp; Line:<span>&nbsp;</span>122<span>&nbsp;</span><br /><br />Stack Trace:<span>&nbsp;</span><br /><br /></p> <table> <tbody> <tr> <td> <pre>[TypeLoadException: Specified payment method class "EPiServer.Business.Commerce.Payment.DIBS.DIBSPaymentGateway, EPiServer.Business.Commerce" can not be created.] EPiServer.Commerce.Order.IPaymentProcessorExtensions.CreateProviderInstance(String className, IOrderGroup orderGroup) +225 EPiServer.Commerce.Order.IPaymentProcessorExtensions.CreatePaymentGatewayInstance(IPayment payment, IOrderGroup orderGroup) +155 EPiServer.Commerce.Order.IPaymentProcessorExtensions.ProcessPayment(IPaymentProcessor paymentProcessor, IPayment payment, IShipment shipment, IOrderGroup orderGroup) +211 EPiServer.Commerce.Order.IOrderGroupExtensions.ProcessPayments(IOrderGroup orderGroup, IPaymentProcessor paymentProcessor, IOrderGroupCalculator orderGroupCalculator) +251 TestProject.CMS.Features.Checkout.Services.CheckoutService.PlaceOrder(ICart cart, ModelStateDictionary modelState, CheckoutViewModel`1 checkoutViewModel) in D:\gitProjects\TestProject-Episerver-Responsive\TestProject.CMS\Features\Checkout\Services\CheckoutService.cs:122 TestProject.CMS.Features.Checkout.Controller.CheckoutController.Purchase(CheckoutViewModel`1 viewModel, String paymentOption) in D:\gitProjects\TestProject-Episerver-Responsive\TestProject.CMS\Features\Checkout\Controller\CheckoutController.cs:201 lambda_method(Closure , ControllerBase , Object[] ) +146 System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +14 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +157 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27 System.Web.Mvc.Async.AsyncControllerActionInvoker.&lt;BeginInvokeSynchronousActionMethod&gt;b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +22 System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) +29 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +32 System.Web.Mvc.Async.AsyncInvocationWithFilters.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3d() +50 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass46.&lt;InvokeActionMethodFilterAsynchronouslyRecursive&gt;b__3f() +225 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass33.&lt;BeginInvokeActionMethodWithFilters&gt;b__32(IAsyncResult asyncResult) +10 System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +34 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass2b.&lt;BeginInvokeAction&gt;b__1c() +26 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass21.&lt;BeginInvokeAction&gt;b__1e(IAsyncResult asyncResult) +100 System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27 System.Web.Mvc.Controller.&lt;BeginExecuteCore&gt;b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +13 System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +36 System.Web.Mvc.Controller.&lt;BeginExecute&gt;b__15(IAsyncResult asyncResult, Controller controller) +12 System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +22 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26 System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10 System.Web.Mvc.MvcHandler.&lt;BeginProcessRequest&gt;b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +21 System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9765121 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously) +155</pre> </td> </tr> </tbody> </table>

It would be much easier to diagnose if we can access your environment. I would suggest you to contact Episerver support service for further assistance.