Add-on Key disruption to traffic

The configuration is reloaded when (after) adding the add on-key. This may cause disruption to services, depends on what kind of services you have configured and how busy those are. So consider to do it at a quiet time. Anyway, I suggest to apply the add-on the license first to the standby unit. Then do a failover, check that all is ok and traffic continues. After that apply the second add on key to the new standby. Finally fail back.