Error when adding section to workplace

I am receiving an error when adding a custom section to a workplace. The custom section works, I can navigate to it manually and the section works fine. However, when I try to add the section to a workplace (any workplace) I get an error when the application posts to /0/rest/WorkplaceService/AddSectionToWorkplace. The payload for this post is correct (it does have the correct ID for my section schema from SysModule and the workplace), but an error 400 is returned with the following error details:

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The server encountered an error processing the request. The exception message is 'Sequence contains no matching element'. See server logs for more details. The exception stack trace is:

at System.Linq.Enumerable.First[TSource](IEnumerable`1 source, Func`2 predicate) at Terrasoft.Configuration.Section.SectionRepository.Get(Guid sectionId) at Terrasoft.Configuration.Workplace.WorkplaceManager.AddSectionToWorkplace(Guid workplaceId, Guid sectionId) at SyncInvokeAddSectionToWorkplace(Object , Object[] , Object[] ) at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs) at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc) at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

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How can I find out what is missing for my section to correct this? I've tried building the entire configuration, modifying the section again in the section wizard, etc, still no luck. Any ideas?