unable to have turbo form after upgrading CRM 2011 to CRM 2016 (8.2)

Hi,

I'm not able to enable the new rending (turbo form) on all my entities (ie contact, account, ...) after upgrading crm instance (on premise) from CRM 2011 to CRM 2016.

I've added a new script to check  it turbo form is enabled  :
var turboFormsEnabled = Xrm.Internal.isTurboForm();
alert(turboFormsEnabled );

this script always return false.

the use of legacy forom rendering is OK.

what should i do to get the turbo form enabled;

Thanks for you help.