Welcome to the family and sorry for the issue you are having with the plugin!
We’ve just looked into this and it seems that you are using an older PHP version, which makes the plugin incompatible with your setup. You will need at least PHP 5.4 active on your server to make sure the plugin works 100%.
We would strongly recommend getting in touch with your hosting to confirm that and request an upgrade. It’s not just for the plugin’s benefit. Having that old PHP version installed on the server opens your website to potential attacks and vulnerability exploits.
If you need any hand with that, please do let us know. Always happy to help 😉