Search has encountered a problem that prevents results from being returned

​When you see the following message displayed in search related webparts or in the search centre:

Search has encountered a problem that prevents results from being returned. If the issue persists Please contact your administrator

Correlation ID:

Or in Dutch:

Bij het zoeken is een probleem opgetreden dat verhindert dat resultaten worden geretourneerd. Als het probleem zich blijft voordoen, neemt u contact op met de beheerder

Correlation ID:

The Search Administration shows a warning icon at the Index partition section:

And in the ULS the following messages can be found:

• Microsoft.Ceres.InteractionEngine.Component.FlowHandleRegistry : Exceptions occurred when evaluating the flow.  Microsoft.Ceres.Evaluation.DataModel.EvaluationException: Cannot plan query for index system SPd90968e26d35. Index fragment ‘0’ has no available cells. Cell statuses: [Cell I.0.0 on node IndexComponent1: Cell status is set to ‘not available’ (cell out of sync or seeding)]   at Microsoft.Ceres.Evaluation.Engine.ErrorHandling.HandleExceptionRecordSetSink.DoWithTryCatch(IRecord record)  at Microsoft.Ceres.InteractionEngine.Component.FlowHandleRegistry.SubmitData(FlowExecutionInfo handle, InputData inputData, Stopwatch timer, String correlationId, Guid tenantId, String query, String flowName, Int32 queryTimeoutMillis)  at Microsoft.Ceres.InteractionEngine.Component.FlowHandleRegistry.ExecuteFlow(String flowName, InputData input, Int32 queryTimeoutMillis)
• w3wp.exe: All query processing components are in ‘Failed’ status.
• SearchServiceApplicationProxy::Execute–Error occured: System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]: Tried IMS endpoints for operation Execute: Cannot plan query for index system SPd90968e26d35. Index fragment ‘0’ has no available cells. Cell statuses: [Cell I.0.0 on node IndexComponent1: Cell status is set to ‘not available’ (cell out of sync or seeding)] (Fault Detail is equal to An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is: Microsoft.SharePoint.SPException: Tried IMS endpoints for operation Execute: Cannot plan query for index system SPd90968e26d35. Index fragment ‘0’ has no available cells. Cell statuses: [Cell I.0.0 on node IndexComponent1: Cell status is set to ‘not available’ (cell out of sync or seeding)] at Microsoft.Office.Server.Search.Query.Ims.LoadBalancer.RoundRobinLoadBalancerContext.NextEndpoint(String operationName, String failMessage)  at Microsoft.Office.Server.Search.Administration.SearchServiceApplication._ImsQueryInternalType.DoSpLoadBalancedImsOp[T](ImsBackedOperation`1 imsCall, Int32 timeoutInMilliseconds, Int32 wcfTimeoutInMilliseconds, String operationName)  at Microsoft.Office.Server.Search.Administration.SearchServiceApplication._ImsQueryInternalType.Execute(QueryProperties properties, Guid ssaId)   at Microsoft.Office.Server.Search.Administration.SearchServiceApplication.Execute(QueryProperties prope…).

And the Event viewer shows something like this:

Application Server Administration job failed for service instance Microsoft.Office.Server.Search.Administration.SearchServiceInstance (c15f488e-cc03-4274-a280-72e039cab353).

Reason: An update conflict has occurred, and you must re-try this action. The object SearchDataAccessServiceInstance was updated by <user>, in the OWSTIMER (9208) process, on machine <machine>.  View the tracing log for more information about the conflict.

Technical Support Details:
Microsoft.SharePoint.Administration.SPUpdatedConcurrencyException: An update conflict has occurred, and you must re-try this action. The object SearchDataAccessServiceInstance was updated by <user>, in the OWSTIMER (9208) process, on machine <machine>.  View the tracing log for more information about the conflict.

at Microsoft.Office.Server.Search.Administration.SearchServiceInstance.Synchronize()
at Microsoft.Office.Server.Administration.ApplicationServerJob.ProvisionLocalSharedServiceInstances(Boolean isAdministrationServiceJob)

Solution

To solve the issue follow these steps:

1. Stop the Timer Service
2. Clear the configuration cache
   1. Find in \ProgramData\Microsoft\SharePoint\Config the folder where the file cache.ini exists
   2. Delete every file from this folder EXCEPT cache.ini
   3. Open cache.ini, delete the content and put ‘1’ (without the quotes) in it and save the file
3. Restart the Timer Service
4. Index reset
5. Full crawl

And the Index Partition is healthy again!