SASS Error with Luther

We just noticed a SASS error when trying to activate Luther for a book on our production network (pictured below). Anyone seen this before or have suggestions as to its cause/solution? All other themes can be activated just fine …

It looks like we’re having problems with books where Luther is installed already as well. When I try to visit the admin page for a book where this is installed, I get a Your theme, pressbooks-book, is not installed. Please visit GitHub for installation instructions. error message. For visitors to the book URL, they see a The theme directory "pressbooks-book" does not exist. ERROR: The themes directory is either empty or doesn’t exist. Please check your installation. message. I can manually change the theme information in book settings to a different theme and it works, but something appears to be brokein in our production server. @etienne can you verify by visiting Would you like us to file a ticket with you at Unizin?

Is Pressbooks Textbook installed?

Yes, it is installed.

Can you share the relevant versions of everything? Otherwise I’m just guessing…

Sure. I think we’re running WP 4.9.1. @etienne has access to the server with everything on it (I don’t), but it looks like we’re running PB 4.5.0 and PB Textbook 3.1.6

Here are the themes we have installed on the network: