On purchasing a Mitan Licence, you can choose to use a hardware (USB) dongle. A hardware dongle requires a Windows device-driver to be installed. Installation of the device-driver is done by a utility program that is installed as part of the T-Calc Suite.
The dongle plugs into any USB port. When the USB dongle is inserted for the first time, Windows will start the "found new hardware" process, and unless the "Install USB dongle device driver" step has been done Windows will not find a device driver for the dongle, so the "found new hardware" process will fail and have to be rerun after the device-driver has been instaled.
Installing Mitan Licence Support does not actually install the device driver for the dongle, but just installs a utility to do the device-driver installation. Start the "application selector" by clicking on the T-Calc desktop icon. Then click the "Utilities" tab/button, which wil display a panel with several licence-related buttons. At the top is a button with the text alongside saying "Install device driver...". Underneath this button are some instructions on what options to take when you click the button to start the device-driver installation utility. Click the button and follow these instructions.
If you change the PC date setting to an earlier date, the Licence may no longer work. Restore the PC date to its previous setting or later to enable the Licence to work. In effect the dongle "remembers" the latest system date it has "seen" and will not respond correctly for an earlier system date.