ERPmine

Since my old system had reported a lot of bugs, I thought I would fix them with a completely new system. I am currently feeding the new system with data from 2017.
What works so far
Inventory - Purchasing - Assignment of articles to the individual issues - Book time (ticket and time recording ERPMine)

Now I want to regenerate the old invoices:
I go to: Billing, choose the account and the project, choose the period (e.g. December 2017) and click apply.
It happens - nothing "No dataw to display"
I click "Generate Invoice" - it appears in a new window "No Data to display"
I click on "Unbilled Invoice" - everything appears (almost) correctly there.

How do I generate the invoice now?

And another (small) problem: The tax is only calculated with two digits behind the decimal point ... in Germany, however, it is calculated with 4 digits behind the decimal point (but only displayed with 2)