Still being a newbie at Odoo and another problem!

When we try to make a down payment on a quote, by pressing make invoice, we get a new screen, where we can select multiple options. When we use "Down payment (percentage)" and enter for example 20% we get a permission error saying :

Document type: ir.values, Edit: create

I added the ir.values in settings for our user group but its still not working, are we doing something wrong?

thanks in advance!