Subscribe/Contact not working in IE and Firefox

Firstly thanks for a great free plugin.

URL: http://www.aboutnewent.co.uk

Chrome works pefectly though FF and IE (haven’t tested other browsers) doesn’t:

Subscribe – nothing happens when button clicked.
Contact form – nothing happens when button clicked though email gets sent.

Grateful for help! I’ve tried other solutions listed on the forum. Thanks.

https://wordpress.org/plugins/wp-maintenance-mode/