If the AP is able to ping the controller IP, what is the firmware on the AP and the controller? Make sure the AP is on the standalone version 104.x or 110.x when connecting.
As per Fahrizal's previous comment, system is on a compatible version because he shared the get scg output with SCG service enabled.
rkscli: get scg
------ SCG Information ------ SCG Service is enabled. AP is not managed by SCG. State: CONN_GET_ADDR_STATE Server List: 192.168.1.206 No SSH tunnel exists Failover List: Not found Failover Max Retry: 2 DHCP Opt43 Code: 6 Server List from DHCP (Opt43/Opt52): Not found SCG default URL: RuckusController SCG config|heartbeat intervals: 30|30 SCG gwloss|serverloss timeouts: 1800|7200 Controller Cert Validation : disable