How do I handle a long gap on my résumé? - 4 months and counting

My résumé shows a gap from a layoff and some health issues. This is my first time dealing with any of this. 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.

I was hired after a 4-month gap. The manager said the skills test mattered more than the dates.