Does LoginTC work for services not connected to the internet?

Yes, there are multiple scenarios where LoginTC can be added to serviced not connected to the internet.

First, LoginTC is available completely on-premises with LoginTC Managed:

https://www.logintc.com/on-premises-multi-factor-authentication/

LoginTC Managed does not require any internet connectivity to operate. The solution is self-hosted and brings the MFA platform directly to your infrastructure.

For LoginTC Cloud, internet connectivity is leveraged between the client application and cloud services to deliver secure authentication.

The LoginTC Windows Logon and RDP Connector does have several options for offline authentication:

https://www.logintc.com/docs/connectors/windows-rdp-logon/#offline-logon