If what you're saying doesn't resonate, even though you know they need to hear what you know, they might not be fully ready for the information you have or see it as plainly as you do at the depth at which you're trying to communicate it.
If you feel like you're beating a dead horse, know that this is something you can't change - it's just not time for them to receive this message yet.
It's honorable to try, but for your own peace, you have to know when it's time to let go.