Error on loading forms plugin

Hi

Really keen to keep using your forms, but I’ve recently got this error and had to uninstall

Fatal error: Call to undefined function wp_session_commit() in /home/wimbo809/public_html/wp-content/plugins/planso-forms/index.php on line 115

Any ideas what might cause this?

Thanks

Steve

https://www.ads-software.com/plugins/planso-forms/