Could you please tell us which version of Office 2019 do you want to register?
Such as volumn licensed Office Professional Plus 2019, retail Office Home&Business 2019, or others.
For volumn licensed version of Office, we could use the command to active Office.
Such as for 64 bit Office 2019, the command is cscript.exe "%ProgramFiles%\Microsoft Office\Office16\ospp.vbs" /inpkey:XXXXX"
.
But we could not use command to register or bind a Microsoft account to one Office.
Besides, even if we do not log in to Microsoft accounts, we can still use the activated volume license version of Office 2019 normally.
For retail Office, we need to redeem a new purchase first via going to www.office.com/setup or Microsoft365.com/setup manually, and then sign in with a correct Microsoft account to bind this license.
But this step we do not use command line.
In addition, if we reinstall Office later, we could activate Office via logging into licensed account without a product key.
Hope the information could be helpful.
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