I'm sure there is a lot more to the config that you haven't shown.
Try this:
mkdir -p /var/www/certbot/.well-known/acme-challenge/
echo "Test_File-1234" > /var/www/certbot/.well-known/acme-challenge/Test_File-1234
Then (from Internet):
http://sanyoeng.com/.well-known/acme-challenge/Test_File-1234