SFTP VIP on CLoud F5 AWS not working from internet , from F5 its working

So from packet capture, you see TCP SYN hitting F5 and no response? Nothing is forwarded to the real SFTP server on a server side connection, correct? 
Looks like SYN packet might be dropped, I'd check that packet data in your pcap are actually matching the configuration. 

First thing I'd check is that your network configuration is on point for the client-side connection - eg. F5 has a default route back to client IP, Virtual Server is listening on intended VLAN. 
Next, match the packet from your capture to VS and confirm service port and IP are correct, and client IP belongs to a network that's included in source network list. 

If everything is spot-on, you need to investigate VS secifications further as there might be some profile "conflicting" with your traffic or likely preventing the match, but you said this is a fastL4 so that's quite unlikely imo.

Hi Thanks for your input. We found the issue. Its the AFM and Zone was wrongly marked for the destination. 

Again thanks. 

CA_Valli