WARNING! This method only works on a VMware vSphere 5.5, 6.0 and 6.5 environment.
Make sure that the SSH service is running on your ESXi host.
Open an SSH session to your ESXi host.
Enter the following command.
rm -r /etc/vmware/license.cfg
cp /etc/vmware/.#license.cfg /etc/vmware/license.cfg
The license is again valid for 60 days after the vpxa service is restarted.