When an ESXi management IP address is changed and if it fails to connect to the vCenter then restart vCenter agent and management agents on ESXi host.

Workaround:
Before proceeding, ensure that:

1. The new IP address and required network setup are ready.
2. You have disabled High Availability (HA) in the cluster to prevent a failover event. For more information, see Disabling VMware High Availability (HA) (1008025).
3. Disabled lockdown mode if enabled  For more information, see Enabling or disabling Lockdown mode on an ESXi host.
4. The ESXi host is placed in maintenance mode as the host may disconnect during the change of IP address.

To change the ESXi server management IP address:

1. Change ESXi Server Management IP Address:

Use DCUI Change ESXi Server Management IP Address:

• Log in to the Direct Console User Interface of the ESXi.
• Select Configure Management Network and press Enter
• From the Configure Management Network Options menu, select IPv4 Configuration or IPv6 Configuration press Enter
• Set new IPv4 or IPv6 config then Press Enter
• Press Esc to Exit DCUI pop alert "Configure Management Network: Confirm"
• Press Y to apply changes and restart management network.

• Open a SSH session to the host with root credentials. For more information, see Opening a command or shell prompt (1003892)
• Alternatively, you can also change the IP address from the KVM or the remote console.
• Run this command: esxcli network ip interface ipv4 set -i vmk1 -I ip address -N subnet -t static

2. Update the DNS server entries to reflect the required changes.
3. Restart ESXi  Server Management Network.

Log in to the Direct Console User Interface of the vCenter Server Appliance.
Select Restart Management Network and press Enter.
Press F11.

4. ​Restart the Management agents (vpxa) in ESXi . Please see the detail in https://kb.vmware.com/s/article/1003490
5. Reconnect host to vCenter
6. Login to vCenter Server Web Client and Select a host in the inventory.
7. Right click host and select Connection -> Connect

You can adjust other options to ensure that HA does not activate for a momentary disconnect from vCenter Server instead of a host failure, resulting in failure of virtual machines. For example, the key feature is Datastore heart-beating. If this feature is enabled, virtual machines are identified as running on the ESXi host and HA does not activate. You can also adjust the host monitoring or network isolation responses while making changes.

Note: This is the safest and simplest method:

1. Place the ESXi host in maintenance mode.
2. Remove the ESXi host from vCenter Server.
3. Connect directly using the ESXi Host UI Client or KVM.

• NOTE: Ensure you have console access to the ESXi server before doing the step.