Hey Hugh,
first of all, thank you for the purchase!
I’ve tested the theme with a multisite installation and hasn’t been able to reproduce the mentioned error as of yet; could you please provide access to your back-end, I would be able to find the culprit of the bug much quicker in that case. You can send the login and password, together with the website’s URL, to support@satoristudio.net (no disclosure guaranteed). In case you decide to create a new user, please give the user the “administrator” role so that I can see the code of the theme. Thanks!
Sincerely,
Andrii / Satori Studio