Hello @DarioZanni,
The enable pin of GD3000 must be kept high in order to have the predriver functional. If you need more info about the GD3000 predriver IC, you can take a look here.
I recommend starting using the default model and reading all info that you can find in the model. It is possible that, if you do not connect the motor, the model will raise an error (fault) that can put the GD3000 in sleep mode. Any kind of errors/faults should be seen in the Freemaster project. If you want to be more cautious, you can use a power source with an overcurrent function activated and set it to 2A or 3A.
Best regards,
Adrian