New Book- Some transactions not posting

We created a new financial book.
Added all the segment values, updated the GL Controls, created mapping to the old book, updated the GL Posting rules.

most of the transactions post perfectly.
Transactions tied to documents posted on the old book, do not post.
Its as if Epicor doesnt know what GL account to use.

For example:
Cash receipts for invoices posted in the old book.
It picks the right cash account, but does not pick the AR account.

How do I get Epicor to pick the right GLs?