Failure in negotiate progress IPsec phase 2

[alikahoot]

I have Fortigate v6.4.5, and my peer has Cisco. I have setup an IPSec Tunnel, and I have repeatedly checked the settings, they are the same. Phase1 is up but Phase2 isn't up and it keeps giving error in negotiating progress IPsec phase 2. 

[Toshi_Esumi]

You need to run "IKE debugging". That would tell you, or imply you, what part of phase2 either of them didn't like.

https://kb.fortinet.com/k....do?externalID=FD46611