If the copyright or work or school account isn't working, see I forgot the username or password for the account I use with Office. Add-ins and other extensibility solutions that are compatible with volume licensed versions of Office 2019 will most likely be compatible with Office LTSC 2021 or https://microsoft-office-lizenca97420.bloggosite.com/35226427/5-semplici-tecniche-per-microsoft-office-2021-standard