Download the latest Windows 10 20H2 iso image from media creation tool, then clean install.
https://www.microsoft.com/en-us/software-download/windows10
Completely format disk and clean install will exclude all system related issue, and during oobe phase, you could create a local account and use it as login account. If you worry about MS account, you could login it on website and delete the devices which under this account.
https://account.microsoft.com/devices/
Once installation finished, you can check Store. This process I have used many times, always work.
-------------------------------------------------------------------------------------
If the Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.