Why isn't certbot writing the verification file?

Question

I am trying to install a certificate using certbot on Ubuntu Xenial by using the below command:

sudo certbot run -a webroot -i apache -w /var/www/mydomain/public/.well-known/acme-challenge/ -d "example.com"

I get a challenge failed error with the following notes:

Domain: mydomain.com
   Type:   unauthorized
   Detail: Invalid response from
   http://example.com/.well-known/acme-challenge/lvJ9RbuDyoPn4NXnxPpjOYpsGHZb6ZYdDoBWW-6JC1k

I created the /.well-known/acme-challenge myself thinking this might help, but it didn't. I tried putting a file into the acme-challenge directory and browsed to it through Chrome and this worked without an issue. Therefore, I know the Apache host is setup correctly.

I'm now at a loss of what to try.