If you are trying to use the license of the previous (but still available) DecSoft App Builder, that can't work, in other words, the new DecSoft App Builder requires a different license, Paolo. If you want to purchase a license of the new DecSoft App Builder, contact me, since there is a discount for currently DecSoft App Builder customers. You can also download the previous DecSoft App Builder from your DecSoft customer area, from the "Releases" tab.
Everybody can read the DecSoft support forum for learning purposes, however only DecSoft customers can post new threads. Purchase one or more licenses of some DecSoft products in order to give this and other benefits.