Ah sorry, if you can make a quick update to this file, it will fix the issue:
File: /plugins/vmcoupon/aworewards/aworewards.php, around line 20 is
<?php
if ( method_exists( $this, 'registerLegacyListener' ) ) {
$this->registerLegacyListener( 'plgVmValidateCouponCode' );
$this->registerLegacyListener( 'plgVmCouponInUse' );
$this->registerLegacyListener( 'plgVmRemoveCoupon' );
$this->registerLegacyListener( 'plgVmCouponHandler' );
$this->registerLegacyListener( 'plgVmUpdateTotals' );
$this->registerLegacyListener( 'plgVmCouponUpdateOrderStatus' );
}
?>
And change it to
<?php
if ( method_exists( $this, 'registerLegacyListener' ) ) {
$this->registerLegacyListener( 'plgVmCouponUpdateOrderStatus' );
}
?>
If you cannot do that, to stop the front end error, disable the plugin: VMCoupon - AwoRewards