Activation Error 70: Internal Error

I have a large fleet of 100+ devices, which use Zyxel SecuExtender to connect to an enterprise network. When upgrading these devices to run newer operating systems, we reinstall Zyxel SecuExtender, and try to reactivate the same licenses, which as far as I am aware, were lifetime licenses, or if not, 3-year licenses, not past expiry. I regularly encounter Activation Error 70: Internal Error, and want to get this figured out. We are using SecuExtender v7.7.5008, which looks to be up to date. The issue occurs on managed LAN as well as unmanaged hotspot.