Greetings,
So that it would benefit others, in case they are noobs, like I was, I wanted to update this thread.
There was an issue with the DNS. The certifytheweb application was updating the DNS automatically, all right, but the DNS servers were not configured right and they did not respond to the _acme-challenge.mydomain.com request and that is the reason it was failing.
In case anyone is stuck with this issue, please create a manual entry in your DNS like the following, as suggested by webprofusion :
TXT Record
_validation-test.mydomain.com → ‘hello world’
Then visit https://toolbox.googleapps.com/apps/dig/#TXT/
and enter
_validation-test.mydomain.com
press ‘TXT’ button
It should respond back with ‘hello world’
You can also use tools like
dig -t TXT _validation-test.mydomain.com
OR
unboundtest.com
OR
https://dnschecker.org/#TXT/_validation-test.mydomain.com
Hope this helps
Thank you Webprofusion for all the support and guidance.
Manish Naik