Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If the problem happened after you upgraded to MAC OS X 'El Capitan', then you probably either need to get a driver for El Capitan specifically, or at minimum, to remove the current driver and install it over again in the El Capitan context.
But tell me more about the problem... the solution might be different from the above.
If I obviously do not have an answer, then I suspect that passing the case to another Expert here would be appropriate, so I have Opted Out, not cutting off communication, cut opening the case to another Expert at no additional charge to you.