I'm currently trying to update our website from V7.6.5 to V8.6.1. I had to upgrade the Database through a couple of other versions before I could get the site to load. The site itself now loads however when I go into the back office and try to view or modify the data types I get the following error:

Unhandled controller exception occurred for request '"http://localhost:2593/umbraco/backoffice/UmbracoTrees/DataTypeTree/GetNodes?id=-1&application=settings&tree=&use=main&culture="'

System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary. at System.Collections.Generic.Dictionary2.get_Item(TKey key) at Umbraco.Web.Trees.DataTypeTreeController.<>c__DisplayClass2_0.<GetTreeNodes>b__5(IEntitySlim dt) at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() at System.Collections.Generic.List1.InsertRange(Int32 index, IEnumerable1 collection) at Umbraco.Web.Trees.DataTypeTreeController.GetTreeNodes(String id, FormDataCollection queryStrings) at Umbraco.Web.Trees.TreeControllerBase.GetNodes(String id, FormDataCollection queryStrings) at lambdamethod(Closure , Object , Object[] ) at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>cDisplayClass62.

@MessageTemplate : Unhandled controller exception occurred for request '{RequestUrl}'

RequestUrl : http://localhost:2593/umbraco/backoffice/UmbracoTrees/DataTypeTree/GetNodes?id=-1&application=settings&tree=&use=main&culture=

SourceContext : Umbraco.Web.Trees.DataTypeTreeController

Any ideas on how to fix this?

Thanks