I could not reproduce this in my test website. Do you have any more code for this plugin in your website?
Can you please give me access to your website so that i can try in your website? If yes please use https://www.shamimsplugins.com/sensitive-information/ (provide Website Admin and user credentials)
Please test now.
You added code in snippets plugin. Also you loaded that code only in front-end. But this plugin send message using ajax. All admin ajax load admin code also. I changed that settings to load both in front-end and back-end. Now it is working.