I have the same problem.
If I show the errors, this will appear:
Fatal error: Uncaught TypeError: basename(): Argument #1 ($path) must be of type string, array given in /htdocs/www.site.com/wp-content/plugins/cost-calculator-contact-form-7/admin/cf7costcaloc-cf7-panel.php:241 Stack trace: #0 /htdocs/www.site.com/wp-content/plugins/cost-calculator-contact-form-7/admin/cf7costcaloc-cf7-panel.php(241): basename(Array) #1 /htdocs/www.site.com/wp-includes/class-wp-hook.php(309): cf7costcaloc_cf7_panel->save_application_form(Object(WPCF7_ContactForm)) #2 /htdocs/www.site.com/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array) #3 /htdocs/www.site.com/wp-includes/plugin.php(522): WP_Hook->do_action(Array) #4 /htdocs/www.site.com/wp-content/plugins/contact-form-7/includes/submission.php(619): do_action_ref_array('wpcf7_before_se...', Array) #5 /htdocs/www.site.com/wp-content/plugins/contact-form-7/includes/submission.php(86): WPCF7_Submission->before_send_mail() #6 /htdocs/www.site.com/wp-content/plugins/contact-form-7/includes/submission.php(27): WPCF7_Submission->proceed() #7 /htdocs/www.site.com/wp-content/plugins/contact-form-7/includes/contact-form.php(1042): WPCF7_Submission::get_instance(Object(WPCF7_ContactForm), Array) #8 /htdocs/www.site.com/wp-content/plugins/contact-form-7/includes/controller.php(25): WPCF7_ContactForm->submit() #9 /htdocs/www.site.com/wp-includes/class-wp-hook.php(305): wpcf7_control_init() #10 /htdocs/www.site.com/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array) #11 /htdocs/www.site.com/wp-includes/plugin.php(522): WP_Hook->do_action(Array) #12 /htdocs/www.site.com/wp-includes/class-wp.php(396): do_action_ref_array('parse_request', Array) #13 /htdocs/www.site.com/wp-includes/class-wp.php(758): WP->parse_request('') #14 /htdocs/www.site.com/wp-includes/functions.php(1310): WP->main('') #15 /htdocs/www.site.com/wp-blog-header.php(16): wp() #16 /htdocs/www.site.com/index.php(17): require('/htdocs/www...') #17 {main} thrown in /htdocs/www.site.com/wp-content/plugins/cost-calculator-contact-form-7/admin/cf7costcaloc-cf7-panel.php on line 241