If your workflows are working just fine, but you are unable to get UI-access to the workflows in SharePoint, because if this error:

Sorry, something went wrong

Method ‘StartWorkflowOnListItem’ in type ‘Microsoft.SharePoint.WorkflowServices.FabricWorkflowInstanceProvider’ from assembly ‘Microsoft.SharePoint.WorkflowServices, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c’ does not have an implementation.

and your ULS logs gives your these errors:

Application error when access /_layouts/15/Workflow.aspx, Error=Method ‘StartWorkflowOnListItem’ in type ‘Microsoft.SharePoint.WorkflowServices.FabricWorkflowInstanceProvider’ from assembly ‘Microsoft.SharePoint.WorkflowServices, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c’ does not have an implementation

System.TypeLoadException: Method ‘StartWorkflowOnListItem’ in type ‘Microsoft.SharePoint.WorkflowServices.FabricWorkflowInstanceProvider’ from assembly ‘Microsoft.SharePoint.WorkflowServices, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c’ does not have an implementation

You need to apply one or both of these steps in order to get your Workflows back online for viewing

Step 1

Install this hotfix to get the STS and OServer at the same path level: http://support.microsoft.com/kb/2880963 (Remember to do this with to SharePoint Install account)

Restart the Microsoft SharePoint Foundation Workflow Timer Service in manage services (Central admin) on server under application management

Step 2

If that ends up with giving you another error along the lines “Something went wrong. To try again, reload the page…” take a look at the Eventviewer (Applications and Services Log\Microsoft-Workflow\Operational) and look for this warning:

Failed SQL command after 1 tries with error ‘229’. Exception: System.Data.SqlClient.SqlException (0x80131904): The EXECUTE permission was denied on the object ‘InsertTrackingAndStatus’, database ‘SP2013_WF_InstanceManagement’, schema ‘dbo’.

…..

FIX

Go to your databases and assign the “workflow service account” (“domain\SPWorkflow” in my case) the “db_owner” permissions in your database “SP2013_WF_InstanceManagement”. Check the eventlog message for further databases. You might need to do the same on “SP2013_WF_ResourceManagement_DB” as well.