That is not a subdomain of razu.mov. But what error do you get when trying to renew the certificate? Because the one you posted is one you'd get from trying to visit that site (which I don't get when I visit it), not an error from Let's Encrypt or any ACME client.
Moreover, the cert for razu.mov isn't yet due for renewal. So what's actually going on?
Edit: I do see that the ssllabs report indicates incompatibility with some very old desktop and mobile OSs. So the OS and browser version might also be relevant.