Encountering connectivity issues when attempting to connect to the target host may result from the following scenarios:

The target host is not reachable, leading to issues with UNC validation path validation (admin$).

Difficulties in accessing the Windows Management Instrumentation (WMI) of the target host.

For Cause 1: Unreachable Target Host - UNC Validation:

1. Confirm UNC Validation:

1. Manually verify admin$ share access from the machine where VembuBDR or VembuVMBackup is installed.
2. Run 'cmd' and enter: \\IP\admin$
3. Replace 'IP' with the hostname or IP of the target machine (Example: \192.168.100.100\admin$).
4. Ensure the target host is reachable and added to your Network Address Translation (NAT) gateway.
   

Note: Make sure the target “HostName\IP” you are trying to use is added into your network address translation(NAT) gateway.

2. Firewall Configuration:

1. Make sure your firewall doesn't block remote connections.
2. Add an inbound rule in the target machine's firewall settings:
   
1. Open Control Panel.
2. Navigate to System and Security > Windows Firewall > Advanced Settings.
3. Click Inbound Rules.
4. Create a new rule and select the "Remote Service Management" predefined option.
   
5. Enable the rule and finish the setup.
   

3. Ensure Services are Running:

1. Verify that the following services are running on the target machine:
   
1. Server Service
2. Windows Remote Management (WS-management)
   
3. Cluster Service
   

For Cause 2: WMI Access Issue:

1. Firewall Configuration:

1. Ensure that the firewall isn't blocking Windows Management Instrumentation functions.
2. Add an inbound rule in the target machine's firewall settings:
   
1. Open Control Panel.
2. Navigate to System and Security > Windows Firewall > Advanced Settings.
3. Click Inbound Rules.
4. Create a new rule and select the "Windows Management Instrumentation" predefined option.
5. Enable the rule and finish the setup.
   

2. Ensure Services are Running:

1. Confirm that the following services are running on the target machine:
   
1. Windows Management Instrumentation
2. Cluster Service
   

Confirmation Test:

After verifying the solutions, perform a pre-test using the WBEM utility:

1. Open "wbemtest" on your server/client machine.

2. In the namespace text box, provide the target hostname/IP: \IP\root\cimv2 (Example: \192.168.100.100\root\cimv2).

3. Provide the username and password, and click connect. 

 Note: For local machines, no username or password is required.

4. If issues persist, recheck the solutions and wait for a successful WBEM test result.

5. Once successful, proceed to add the desired host.