[Plugin: Contact Form 7] Emails sent fine but success msg not being displayed.

When i press submit in my contact forms, emails are sent fine and even received instantly but the problem is that the circle which starts revolving after pressing submit do not stop and so Message sent successfully is not being displayed.

Because of this the validation errors are also not being displayed as the circle don’t stop at all.

Although there is no problem in sending email but it cause confusion to the users as whether the message is sent or not.

Please tell me what is the problem.

Thank you
Mahen