PayPal isn't working.

It worked before Christmas, today people are trying to use PayPal and it's throwing a configuration error. This is all that's visible in the logs.

Wed, 06 Jan 2016 21:36:00 +0000 (Severity: 2)
(removedIP) - https://saturdaymornings.co/checkout/151/
ErrorException
4096: Argument 2 passed to IPS\nexus\Gateway\_PayPal::_getAddress() must be an instance of IPS\nexus\Customer, none given, called in /home/saturd60/public_html/applications/nexus/sources/Gateway/PayPal/PayPal.php on line 917 and defined
#0 /home/saturd60/public_html/applications/nexus/sources/Gateway/PayPal/PayPal.php(813): IPS\IPS::errorHandler(4096, 'Argument 2 pass...', '/home/saturd60/...', 813, Array)
#1 /home/saturd60/public_html/applications/nexus/sources/Gateway/PayPal/PayPal.php(917): IPS\nexus\Gateway\_PayPal->_getAddress(Object(IPS\GeoLocation))
#2 /home/saturd60/public_html/applications/nexus/sources/Gateway/PayPal/PayPal.php(416): IPS\nexus\Gateway\_PayPal->_getTransactions(Object(IPS\nexus\Transaction))
#3 /home/saturd60/public_html/applications/nexus/sources/Gateway/PayPal/PayPal.php(299): IPS\nexus\Gateway\_PayPal->_paypalAuth(Object(IPS\nexus\Transaction), NULL)
#4 /home/saturd60/public_html/applications/nexus/modules/front/checkout/checkout.php(1083): IPS\nexus\Gateway\_PayPal->auth(Object(IPS\nexus\Transaction), Array, NULL, Array)
#5 [internal function]: IPS\nexus\modules\front\checkout\_checkout->_pay(Array)
#6 /home/saturd60/public_html/system/Helpers/Wizard/Wizard.php(156): call_user_func(Array, Array)
#7 /home/saturd60/public_html/applications/nexus/modules/front/checkout/checkout.php(143): IPS\Helpers\_Wizard->__toString()
#8 /home/saturd60/public_html/system/Dispatcher/Controller.php(94): IPS\nexus\modules\front\checkout\_checkout->manage()
#9 /home/saturd60/public_html/applications/nexus/modules/front/checkout/checkout.php(62): IPS\Dispatcher\_Controller->execute()
#10 /home/saturd60/public_html/system/Dispatcher/Dispatcher.php(129): IPS\nexus\modules\front\checkout\_checkout->execute()
#11 /home/saturd60/public_html/index.php(13): IPS\_Dispatcher->run()
#12 {main}