Hi,
and sorry for my late answer. The situation has changed a lot.
While uninstalling addons that I no longer use, I fortuitously noticed that after uninstalling some of them, T4 PB started working properly.
For safety, I carried out this procedure both on the public site and on a local version of the site and in both cases it seems that a newsletter component was in conflict. I repeated the operation of disabling and enabling the component several times, and every time I enabled it T4 PB didn't work. Indeed, disabling this component all t4 PB started to work properly.
I then updated the component to the latest version and T4 PB continues to work.
It seems all so strange......... but at this time T4 PB works properly.