Device Access Protocol
Before adding devices supporting ISUP 2.6/4.0 to the system, you need to set the related configuration to allow these devices to access the system.
In the top left corner
of Home page, select 
> Basic Management > System.
Select on the left.
Check Access via ONVIF Protocol.
Switch on Allow ISUP Registration.
Check Allow ISUP of Earlier Version.
Note:
The device may be attacked when accessing the system via ISUP of earlier versions.
Click Save.