Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
1
You indicate you have no access to the original Email account, please provide more information on that, do you not have access to the Microsoft account your Microsoft 365 subscription is linked to?
2
Open Word, go to File - Account.
On that window, you should see the Email address of the Microsoft account used for the subscription, is that the account you can no longer access, and if so, what happened to that account that it is not longer accessible.
If you are using an Apple Mac device, open Word, then at the top, click Word - About Word and on the resulting dialog, in the 'Belongs To' section, you will find the Email address.