Are you accessing System Restore from inside the recovery environment, is that where your password is not being accepted?
If so there is a known bug in the recovery environment where a Microsoft account password does not work, it semes to be caused by not being able to access the Internet in the recovery environment to check the password.
1
If you are able to get into Windows, create a new user account as a local account and do not add a password to the account, you should then be able to perform the system restore form inside the recovery environment.
2
Otherwise, if you are still blocked by a password, you will need to create a bootable Windows 10 USB on another working PC and boot your PC from that, then rather than installing Windows 10, select ‘Repair this Computer’ that will give you access to the Recovery Environment from there
In the Recovery Environment on the USB, you will not be blocked by a password and can perform the system restore.
Click this link: https://www.microsoft.com/software-download/windows10
to download the Media Creation Tool (Click on Download Tool Now), with that you can create a bootable USB flash drive (min 8GB) using that tool.
Then, Boot your PC from the Installation Media you just created.