We have recently installed this plugin to add sagepay payments to the invoicing system and upon getting to the /wpi-checkout/ page, we receive a php error, I checked the logs and this was the result:
PHP Fatal error: Call to undefined function mcrypt_encrypt() in /var/www/fuse/live/html/web/wp/wp-content/plugins/wpinv-sagepay-payment/includes/SagePay.class.inc on line 560, referer: https://www.almcollege.org.uk/wpi-checkout/
I had a quick google and it looks like mcrypt_encrypt() has been deprecated.
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