Hi Souravbswas4,

Thanks for posting in our community.

As your description, you have registered a trial account, but you cannot download Office 365 for business standard from www.office.com.

It seems that you do not have license to download the Office.

If you register account just now, you should wait for a while, it could take some time to change the setting.

If not we suggest you go to Subscription from this page you provided.

Then please check if you have the license with The latest desktop of Office.

If you do not have, you should assign the license to this account.

If you have, you can also reassign the license again. And here are the steps.

1. Please go to www.office.com and sign in with your admin account.
2. Go to admin center->Users -> Active users->click the account you are using.

      3. Then add the licenses for this account.

      4. Please Save changes and sign in again after a while to check if you can download.

Please post back if problem persists and give us some screenshots about your subscription, we will try our best to help you.

Regards,

Jason