1) Check and Warning message for minimum php 5.3.0 version requirement added and if PHP version is less than 5.3.0 the payment opion is disabled on frontend.
2) Fixed the scope operators scope=user_read+invoice_read_write and remove merchant_read (file catalog/includes/modules/payment/gocoinpay.php)
3) Fixed validations and display of messages & log error (file /includes/modules/payment/gocoinpay.php)
1) Change in GoCoin Configration Setting in admin
2) Change in User Authontication while invoice creation
3) Change in Signature and hash creation validation
4) Change in payment validation and log the event