After installing SF7 (v18.0.4) I didn’t experience this error but after updating to v18.0.5 it has returned. I do remember however when this same issue surfaced with SF6 (Yosemite) the only fix was to install another update that was released by Extensis.
Sorry to hear you are again experiencing this issue. It could be a number of things and I would suggest entering a Support Ticket with the link below, as these forums are peer-to-peer and not monitored by our tech support.
In the meantime you can also check out our KBA’s for more detail about that OS activation error:
Give the steps in the linked article a try as well so when you talk to Technical Support you can give them all the info and they will be able to help you.
Thanks for using Suitcase Fusion!