Kubernetes can throw this error at you when the automatic HTTPS fails.
I cannot with certainty say that this solution helps you, but I would recommend that you try to delete your autohttps pod if you have enabled HTTPS. This will cause the autohttps service to restart, which will update your SSL certificate. If the automatic HTTPS was the problem, then this solution will fix it.
For more details, see the end of this post: Trouble getting HTTPS / letsencrypt working with 0.9.0-beta.4 - #5 by matthew.brett