No success message sending email

Hi,

I use a shortcode in a page.
When users subscribes the success message doesn’t appears. All the time is loading and nothing happens, if I click on send button twice an alert appears saying: your already register.
I receive the subscription email the second time and user registration is done correctly.

But the first time when user send the email nothing happens (loading all the time).

And second question is I can’t change [DEFAULT_FROM_NAME] from transactional templates. In fact I’ll change it but not take effect, always appears my personal name.

Thanks in advance.

https://www.ads-software.com/plugins/mailin/