1. Check user's access rights – the flag 'Execute commands' is required.
   
2. Check if the command is written in unit properties (on the 'Commands' tab). In the properties of the command itself, see which rights are required for execution and check whether the user has such rights.
   
3. If the command is executed through TCP or UDP, it is necessary that the unit was connected at the moment of execution. So, you need to wait when it connects.
   
4. If the command is executed through GSM channel, the user is supposed to have rights to send SMS messages (the flag 'Can send SMS' in user properties + the appropriate service in billing plan) and a phone number in the international format should be present in unit properties.
   

It is also possible that commands for your type of device are not supported in gTrack. In this case, send a request to support@gtrack.com.mm with detailed description of those commands. See the list of standard commands.