What does "There is no cover if you are diagnosed with COVID-19 or develop symptoms of COVID-19 within 72-hours of purchasing your policy" mean?

This means that your COVID-19 benefits will start 72 hours after you buy your policy and not immediately after your policy is issued.

For example: 

1. You buy your policy 2 days before you're due to depart for your trip 

If you're diagnosed with COVID-19 the day after you buy your policy and have to cancel your trip, there would be no cover for your cancellation expenses because your COVID-19 benefits have not started yet.

2. You buy your policy 14 days before you're due to depart for your trip 

If you're diagnosed with COVID-19 the day before you're due to depart, you would have cover for the cancellation costs that you incur if you're not able to leave for your trip, because your COVID-19 benefits started 11 days ago

Cover is subject to the policy terms, conditions, limits and exclusions in the Product Disclosure Statement (PDS).