This article explains the procedure to fix if the managed device does not display the Network Topology for Monitored Devices
A few probable causes for this issue are as follows:
1. Please make sure the device is synchronized to the Network Monitoring >> Node list
2. The next action is to confirm that the device end has the LLDP protocol enabled.
set protocols lldp interface all
3. If the issue persists, please get in touch with JTAC support for further assistance