After checking nozzle performance and determining that automatic printhead maintenance is necessary, perform the following procedure.
In most cases a non-working nozzle is temporary and should be resolved through Dry Printhead Swabbing Procedure and/or the standard AMS procedure. Dry swabbing removes debris from the nozzle plate, whereas the Standard AMS deals with trapped air inside the nozzle channel.
Many times a nozzle will recover on its own during printing. If a nozzle does not recover from Dry Printhead Swabbing or Standard AMS practices it may be necessary to recover the nozzle by the procedure: Manual Ink Purge and Printhead Swabbing.