I have seen this 'do not balance' error on my General Journals and other journals in AX. This is the first time that I've seen it when posting a Project Invoice Proposal.
The transactions on voucher [VOUCHER] do not balance as per 10/30/2020. (accounting currency: 0.21 - reporting currency: 0.00)
The Currency on the Proposal is USD, however, the accounting currency is GBP. I know these can be misleading when discussing currencies, but wanted to put it out there.
EDIT:
I just confirmed that this Legal Entity doesn't have a reporting currency setup.