Thank you. Glad it solve your issue.
I have found a topic in your mentioned plugin which explain it. It is for Contact form 7 but may be same issue here. https://wordpress.org/support/topic/conflict-with-contact-form-7-4/#post-9535815 . You can try same solution if your want. (instead of “contact-form-7” use “front-end-pm” in the url)