Firewall stuck

Hi

I have SRX 3600 firewall. It gets stuck at => prompt. I set env settings (e.g. ipaddr, serverip, subnetmask) and then try to load the loader to upgrade new device firmware via tftp. But device failed to load the loader and firewall continously stuck at "=>" promt. How can I troubleshoot the issue. Need help. 

Regards

Arslan