AWS RDS - SQLSTATE[HY000] [1130] Host 'ec2-ip' is not allowed to connect to this MySQL server

My Laravel(hosted on EC2) app database(Mysql) is hosted in AWS RDS it was working fine but now it gives the error "SQLSTATE[HY000] [1130] Host 172...*** is not allowed to connect to this MySQL server, for every API call. I can't connect db to run any SQL query (like SHOW GRANTS) and change the security inbound and add this IP Address( 172...***/32) . VPC is the same for both EC2 and RDS. Some suggest to run this

mysql -h rdsendpoint -u admin -p

but I am unable to connect same error(1130). where is the problem occured in AWS RDs configuration, it was working fine till yesterday