Hi,
GT% seems to be initiator and failing in message 6, cisco phase 1 is fine. Most probably it's ID mismatch so GT5 is failing in the peer auth. Can you please check below :
1: What ids have you configured on the GT5 e.g:
-> set ike gateway test address x.x.x.x?
id Peer ID <-- Cisco is supposed to send this ID, and should match with this config. e.g. IPs, certs etc.
local-id Local Identity (optional) <-- GT5 will send ID, by default it's source interface IP. This looks fine as Cisco is completing the phase 1.
2: Step 1 should fix the issues however, you can try reconfiguring the PSK on both the nodes.
Thanks,
Vikas