Dear Andrew83!
Configuring the interconnection between the ONT and the TR-069 requires creating a WAN interface. In addition, Service List of the WAN interface must contain the TR069
1) Create a WAN Connection on ONT (Routing+Vlan 507+DHCP):
In the navigation tree on the left, choose WAN > WAN Configuration. In the pane on the right, click New. In the dialog box that is displayed, set Parameters as shown below:

Click Apply.
ONT should receive the IP through DHCP after this step. Check Status at System Information > WAN Information. In the pane on the right, you can view the status of the WAN interface.

2) Next Configure TR069 settings for Remote Management from ACS:
In the navigation tree on the left, choose System Tools > TR-069. In the pane on the right, set the parameters related to the interconnection between the ONT and the TR-069 server

Click Apply.
After this step, ONT can be managed from the ACS server.
Thanks!