What did you mean when you said " wrote down the enrollment URL in MC apps (while use close network)".  Is there any typo?  Please elaborate your situation.

i mean i use the enrollment URL to enroll it, since enrollment ID is something processed in SOTI server, so i can't enroll with enrollment ID. sorry for confusing definition.

basically i write it down the enrollment URL, and press the press the button "Enroll", then nothing happened, so i change from Close Network to Open WIFI just to test, and the device enroll to SOTI.

The answers depend on what device platform(s) and what device modes are used.  Some functionalities may not be available if your MobiControl server as well as your devices are restricted to a closed coporate network.

Whether or not it works also depends on how you configure your MobiControl server with MCadmin utility.  

You likely need to provide more details on your server configuration, certificates, device platforms/modes/firmware versions, etc. before anyone can comment for a closed network implementation.   

Frankly speaking, I personally think that it is less and less practical to totally restrict your server and devices to a closed corporate network if most of the useful enteprrise-level functionalies are needed, mainly because the major platform owners (Google for Android Enteprise, Apple for iOS, and Microsoft for Windows) provide various services and mechanisms to ensure security and authentication.