[Forminator Pro] Forminator Error

I just created and installed a form using Forminator Pro, but got an error message after submitting the form: Please advise

Error:

Fatal error: Uncaught Error: Call to undefined function WP_Filesystem() in /home3/joblarde/public_html/trustmypetsitter/wp-content/plugins/forminator/library/abstracts/abstract-class-front-action.php:153 Stack trace: #0 /home3/joblarde/public_html/trustmypetsitter/wp-content/plugins/forminator/library/modules/custom-forms/front/front-action.php(351): Forminator_Front_Action->handle_file_upload('upload-1':wink: #1 /home3/joblarde/public_html/trustmypetsitter/wp-content/plugins/forminator/library/modules/custom-forms/front/front-action.php(99): Forminator_CForm_Front_Action->handle_form('3974':wink: #2 /home3/joblarde/public_html/trustmypetsitter/wp-content/plugins/forminator/library/abstracts/abstract-class-front-action.php(58): Forminator_CForm_Front_Action->handle_submit() #3 /home3/joblarde/public_html/trustmypetsitter/wp-includes/class-wp-hook.php(286): Forminator_Front_Action->maybe_handle_submit(Object(WP)) #4 /home3/joblarde/public_html/trustmypetsitter/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters('', Array) #5 in /home3/joblarde/public_html/trustmypetsitter/wp-content/plugins/forminator/library/abstracts/abstract-class-front-action.php on line 153