Thank you so much @Michael
I had uninstalled the plugins 5 times, but following your instructions I have uninstalled all the plugins again and activated only those that are required, without any additional and fortunately it has worked again.
In case it happens to someone else, the new plugins suggested by themefusion have not been installed.
I have not installed
Fusion White Label Branding
Advanced Custom Fields PRO
Jetpack by WordPress.com
I think one of these plugins created the conflict.
Reply To: Fusion builder desn´t workPMargui2018-06-12T23:46:53+00:00