Microsoft — Office Home & Student 2019 deactivated

Purchased Office home & student 2019 on 27 Jan 2020 from retailer at Kolkata. Installed in Mac on the same day by the retailer. Had difficulty in using the same as it was showing licence is not available. Try alternative account. When used the same user id and password with alternative account, it got activated temporarily for the session. Once the computer is switched off, it got deactivated and required reactivation every time for reuse of it.
I raised this issue with customer service over phone and via email. However, it never got rectified. It forced me to use it with repeated reactivation. Could not contact retailer because of lockdown and covid pandemic
Your system is currently not allowing further reactivation.
This is a item for lifetime use and all the problems, I am facing, are not due to my fault.
My email id: [protected]@hotmail.com/[protected]@gmail.com. Mobile [protected]