Is the macbook also the webserver?
It sounds like it is not, the response certbot says it got from the webserver looks like the start of an error page.
In this thread https://community.letsencrypt.org/t/single-certificate-for-sub-domains-pointing-to-different-ip-addresses/21764/7 I have a post where I show how to run certbot from a machine that is not the webserver.
Basically you need to need to mount the webroot so that certbot has write access to it; Then certbot can prove to letsencrypt that it has write access to the webroot.