How do I handle a long gap on my résumé? (update)

My résumé shows a gap from a layoff and some health issues. I have read a lot of threads here and could not find my exact situation. I am not sure how much to explain. Did anyone get past it?

I listed the volunteering and course under the same dates and kept the explanation to a sentence in the cover letter.

Keep your skills fresh and mention anything recent. It shows momentum.