Make sure that the SSH service is running on your ESXi host.
Open an SSH session to your ESXi host.
Run the following commands;
rm -r /etc/vmware/license.cfg
cp /etc/vmware/.#license.cfg /etc/vmware/license.cfg
/etc/init.d/vpxa restart
The license is again valid for 60 days after the vpxa service is restarted.