mysql – Ruby on Rails cannot access production RDS on AWS

I have done rake db:create sucessfully. But rails db:migrate has access errors on the AWS RDS:

Mysql2::Error: Can't create table `llpdn9i88kz3y837`.`comments` (errno: 150 "Foreign key constraint is incorrectly formed")

and

SHOW ENGINE INNODB STATUS;  

Error: Access denied; you need (at least one of) the PROCESS privilege(s) for this operation
SQLState:  42000
ErrorCode: 1227

and

GRANT PROCESS ON llpdn9i88kz3y837.* TO 'n8p1kzg1v9chfcny'@'localhost';

Error: Access denied for user 'n8p1kzg1v9chfcny'@'%' (using password: YES)
SQLState:  28000
ErrorCode: 1045