Certificate validation failed! Redirecting to login

My Ring App will not let me log in. I opened it just now and it displayed a pop message in black overlaying the app screen that has the "Create Account" and "Login" buttons; the message said "Certificate validation failed! Redirecting to login". However, first the screen kept flashing on and off and it was impossible to interact with it; I had to restart my phone to get it to stop. Then, when I tapped "Login" and entered my user name and password, I got the same "certificate validation failed" message and was put back to the login screen.What is going on and how do I fix it?