The new version of Contact Form 7 - 3.7.x to modify the behavior of the class.
Contact form 7 - 3.6: /contact-form-7/includes/classes.php
line 900 (return $wpcf7_contact_form)
Contact form 7 - 3.7 : /contact-form-7/includes/classes.php
line 972 (return $current)
The plugin uses functions calling global $wpcf7_contact_form in Contact Form 7 Dynamic Text Extension line: 58,151,232
In my case, the dynamic fields with obligations does not work, because repressed line 151 makes reference to $wpcf7_contact_form empty.
Please correct the file at line 58,151,232 replacing this:
global $wpcf7_contact_form;
by:
$wpcf7_contact_form = WPCF7_ContactForm::get_current();
https://wordpress.org/plugins/contact-form-7-dynamic-text-extension/