Check your COM port. For computers with a serial port, typically this will be COM 1. But in most instances a USB-to-Serial converter will be used. If you are using Windows, open Device Manager. Under Ports (COM & LPT), you can figure out which port the converter is using.
Also make sure that the port you are using is not being used by another program. Make sure that any Terminal program is closed or disconnected from the COM port you are using.
If you have a version of miniDOTControl v1.09 or earlier, there can is an issue with the program freezing if it cannot connect to the Time server. In versions 1.10 or later, this issue is fixed and the program will connect after 15 seconds. Download the latest version of miniDOTControl from the PME website.