For the free on-premises version of DeviceHub, it only supports 25 devices to be connected and managed at most. Besides, we can create a license for you if you need to expand the number of connected devices.
Step 1: Create and download license
Go to “Settings -> General -> My information -> License” , create and download your DeviceHub activation code and share it with us, and then we can generate a new license for you according to the number of devices you need to expand.
Step 2: Import new license
Go to “Settings -> General -> My information -> License” open the new license which offered by Milesight and click save.
Step 3: Check Max Manageable