From October 13, 2020 onward, only these versions of Office are supported for connecting to Microsoft 365 (and Office 365) services:
Microsoft 365 Apps for enterprise (previously named Office 365 ProPlus) Microsoft 365 Apps for business (previously named Office 365 Business) Office LTSC 2021, such as Office LTSC Professional Plus 2021 Office 2019, such as Office Professional Plus 2019 Office 2016, such as Office Standard 2016 Note:
Office 2019 and Office 2016 will be supported for connecting to Microsoft 365 (and Office 365) services until October 2023.
Note: Client software: To support tenant restrictions, client software must request tokens directly from Azure AD, so that the proxy infrastructure can intercept traffic. Browser-based Microsoft 365 applications currently support tenant restrictions, as do Office clients that use modern authentication (like OAuth 2.0).
Reference:
https://docs.microsoft.com/en-us/deployoffice/endofsupport/microsoft-365-services-connectivity
https://docs.microsoft.com/en-us/azure/active-directory/manage-apps/tenant-restrictions