This plugin broke my Admin panel

I had purchased and installed a theme based on WP Job Manager, and included the plugin for Ninja Forms – updated to the latest version. I followed your directions here for customizing the job application form: https://wpjobmanager.com/document/customising-job-application-process/#section-2. When I installed and then activated WPJob Manager – Contact Listing, I got the following fatal error:
“Fatal error: Call to undefined function ninja_forms_get_all_forms() in /home/content/p3pnexwpnas04_data03/04/3214604/html/wp-content/plugins/wp-job-manager-contact-listing/includes/forms/ninjaforms.php on line 121”

Now my Admin panel is completely broken.

Please advise on how to fix, as well as what the problem is.

Thanks.

https://wordpress.org/plugins/wp-job-manager-contact-listing/