SSRS Reports giving error


The reports on Ax server have suddenly stopped working. The error message we get is:

The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter The InnerException message was 'Element '’ contains data from a type that maps to the name ‘…/XppClasses:SrsReportProviderQueryBuilderArgs’. The deserializer has no knowledge of any type that maps to this name. Consider using a DataContractResolver or add the type corresponding to ‘SrsReportProviderQueryBuilderArgs’ to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer.’. Please see InnerException for more details.

We tried re-installing reporting services, Ax compilation, full CIL generation and DB Sync, but nothing has helped.