Thanks you for your work!

It would be better to say this upfront. I am not blaming you in any way but this would prevent responses such as the parent's (hopefully).

Let them know that they're having an outage. If their monitors aren't telling them so, they might need to host them off-site.

Let's Encrypt is operating normally. If you're having trouble, please post the details on the community forum so that folks can help you out. There is external monitoring in place.