Coveo initial reindex throws "object reference" exception

Question

I have a scenario, using the free Coveo on-prem server, where I've previously set up a QA Azure VM that works fine with the SQL server, Coveo, and Sitecore all on it. Due to certain external databases we're using, we have to use an Azure VM for SQL, so we're tying out production server that we're setting up into the QA box and making QA into a database server for all intents and purposes. After setting up Sitecore on production CM, I installed Coveo CES 7, the search API, and the Coveo for Sitecore package. Since CES is on the box with CM, everything is set for localhost to the various ports, so theoretically it's self-contained.

When I go to Sitecore's control panel to reindex cover_master_index, I get the error below. I'm not sure if this is because the databases for Sitecore are on another server, or if because that other server also has Coveo and there's some kind of interference. The error's rather unhelpful to me, so if anyone has a thought, I'd appreciate it. Thanks.

Job started: Index_Update_IndexName=Coveo_master_index|#Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Coveo.Framework.Caching.FieldsCacheHandler.Add(IEnumerable`1 p_Entries, String p_DataSourceName)
   at Coveo.AbstractLayer.FieldManagement.FieldsHandlerUtility.GetCompleteFieldConfigs(String p_IndexName)
   at Coveo.AbstractLayer.FieldManagement.AdminModuleFieldsHandler.GetSitecoreFields(String p_IndexName, ForeignKeysConfiguration p_ForeignKeysConfiguration)
   at Coveo.AbstractLayer.FieldManagement.AdminModuleFieldsHandler.UpdateFieldSetAndFields(String p_FieldSetName, String p_IndexName, ForeignKeysConfiguration p_ForeignKeysConfiguration)
   at Coveo.AbstractLayer.Communication.CES.AdminModule.SetUpRequirements(String p_ServerUrl, String p_TargetSite, Boolean p_ExpandUsers, ForeignKeysConfiguration p_ForeignKeysConfiguration, IList`1 p_RankingIgnoredFields)
   at Coveo.AbstractLayer.Communication.CES.CESCommunication.InitializeAdminModule()
   at Coveo.AbstractLayer.Communication.CES.CESCommunication.Initialize()
   at Coveo.SearchProvider.AbstractProviderUpdateContext..ctor(ISearchIndexSummary p_IndexSummary, IIndexCommunication p_Communication)
   at Coveo.SearchProvider.ProviderUpdateContext..ctor(ISearchIndex p_Index, IIndexCommunication p_Communication)
   at Coveo.SearchProvider.ProviderIndex.CreateUpdateContext()
   at Coveo.SearchProvider.ProviderIndex.<Rebuild>b__3e()
   at Coveo.SearchProvider.ProviderIndex.TryPerformIndexingOperation(IndexingOptions p_IndexingOptions, Action p_Action)
   at Coveo.SearchProvider.ProviderIndex.Rebuild()
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Sitecore.Reflection.ReflectionUtil.InvokeMethod(MethodInfo method, Object[] parameters, Object obj)
   at Sitecore.Jobs.JobRunner.RunMethod(JobArgs args)
   at (Object , Object[] )
   at Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args)
   at Sitecore.Jobs.Job.ThreadEntry(Object state)

Answer 1

It looks like you are missing the caches/fieldsCache node in the coveo node in your Coveo.SearchProvider.config, as the following:

<caches>
  <fieldsCache type="Coveo.Framework.Caching.FieldsCache, Coveo.Framework" singleInstance="true" />
</caches>

I suspect this error comes from trying to access the field cache that can't be initialized because the node is missing.