Finally it works!
I had to refresh the database in "Error Log" section and then it worked.
Thanks a lot for your help!

Thanks Veni!
The problem is that the plugins are already enable but the list of the "Payments Methods" is empty.
Is it normal?

Hello there!
We have just purchased the Book it! 2 product. We have just registered the product too. But the problem is that when we try to create a new payment method, we can’t do that because the “New” icon isn’t available.
Do you know witch could be the problem?
I attach a screen shot.
Thanks a lot!