Since I subscribed with Microsoft 365 and downloaded the software, I have been having problems to open my documents. I had a previous Microsoft office which I uninstalled but still seems to conflict. I tried call Microsoft and the automated system tells me to go to the website and hangs up. I tried going to the website and followed instructions but still having the same issue. Microsoft's support service needs to improve.
@Sunder Nambiar
Unfortunately, contacting Microsoft by telephone is difficult if you are running consumer (home use) products. (There is phone support for business customers, though.)
Which version of Office are you trying to install and activate? If you still see more than one version in the list of Installed Apps (in Windows Settings), you should uninstall all versions for which you do not have a license.
For more on product activation, see https://support.microsoft.com/en-us/microsoft-365-activation-licensing/office-install/activate-office-for-windows .