First, I know I have done this on prior versions…However.
I am trying to create a new Main Posting book. There is currently a Book marked as the main book, but I need to modify the GL account structure.
when I create a new book, the “Main Book” checkbox is not active for me to select, and the only option for the book is a consolidation book.
Note - the multi-book license is not active.
Any ideas what I’m missing?
You have to ask Epicor for a multi-book trial license and make sure to deactivate. I think this used to work in E9, but was deemed a bug (that it worked) 
Check company configuration, I believe there is selection option to mark a book as Main/Primary
Follow up. I reached out to epicor. This is a known issue in 10. They have a data fix for this that will change to main book in the system.
Here is the CR… it is database specific. CR37772MPS_10_2_500_13
