Sometimes witnessing doesn’t work, even when you do it to the best of your ability and everything initially appears to go swimmingly.
I’m sure you’ve had the experience. I know I have. I used to be a great believer in dialectical arguments and persuasive apologetics. I would study up a storm to answer a question from scripture that I believed might be important to someone’s salvation or growth in Christ.
I’m not saying a good apologetic never works, but there are things even the most polished and articulate argument can’t possibly accomplish.