SendPress SignUp Widget not working

Hi,
I have got a problem with the Widget.
I use it for people signing up to my subscription list.
Now the problem is, when I write data to widget as: First and Last name and email and press Submit button, nothing happens.

Widget doesn’t do anything.
Not sending notification email, no signing user to subscription list, nor writing Thank you message.

It was working before and I didn’t change anything. It just stopped working.
Any ideas or help.
Thanks a lot

https://wordpress.org/plugins/sendpress/