The issue is partially resolved, I found the answer in the thread below:

https://kriesi.at/support/topic/contact-form-not-working-15

However, the issue persists with an old version of Firefox on Mac. I tested it on a machine where I’m running Firefox 16.0.2 and nothing is happening when I click on “Notify Me”. The text boxes disappear but confirmation message does not show nor is the email being sent.