Please follow the below steps when errors are faced related to connectivity for the respective type of Virtualization monitoring.
Verify the host reachability. Try with both Host name and IP address.
Check the port accessibility if it is not blocked by firewall.
Open the Citrix/Xen Center console from the Applications Manager installed machine.
Check whether you can login with the console using the same user that is used for monitoring. If logged in successfully, then try to Add monitor in Applications Manager.
Verify the host reachability. Try with both Host name and IP address.
Check the SSH / Telnet port accessibility if it is not blocked by firewall.
Using PuTTY (or any CLI client), login to the target KVM host and check whether commands can be executed via SSH / Telnet. Try SSH or Telnet mode, which is tried in Applications Manager.
If any issues faced, please resolve that and try to Add monitor in Applications Manager.
Verify the host reachability. Try with both Host name and IP address.
Check the port accessibility if it is not blocked by firewall.
Open the VMware ESXi / vCenter console from the Applications Manager installed machine.
Check whether you can login with the ESXi / vCenter console using the same user that is used for monitoring. If logged in successfully, then try to Add monitor in Applications Manager.
Verify the host reachability. Try with both Host Name and IP address.
Open the Horizon server management console from the Applications Manager installed machine.
Check whether you can login with the console using the same user that is used for monitoring. If logged in successfully, then try to Add monitor in Applications Manager.
Check whether the VMware PowerCLI power shell package is installed in Applications Manager running machine. Check here on how to install the Power CLI package and further configuration required for monitoring.