[Plugin: Contact Form 7] everything works, but when I add file attachment…

Everything works. Contents of message form arrive to my email and I get the confirmation at bottom.

However, the moment I add in the file attachment, for example, [file file-12], the load icon at the bottom does not stop spinning. I stop getting the confirmation messages. I also stop getting error message when a required field is not filled in. However, I still get the file attachments and everything from the form into my email. It’s just that the user can’t see that the send was successful.

When I take out file attahchment, everything works properly again. I get confirmation messages at bottom and it shows a message when a required field is not put in.

Please help!

Thank you!