404 error after form submission

[deathlyhallows-horcrux]

I installed this plugin and gave API credentials in the settings. When I submit the form I am redirected to a 404 page saying it cannot find the file path to DotmailerNewsletterSubscribe.php. My observation I don't see the plugin file in developer tool under sources tab > wp-content>plugins. when I load my website. I see it after the form submission and 404 error.

Can you please help me fix this problem ASAP?

[tliesnham]

Thanks for making me aware of the issue. I'll take a look at it as soon as possible, and let you know once it's fixed.