IP sec phase 1 error

You need to run debug from FG CLI:

diagnose debug application ike -1
diagnose debug application fnbamd -1
diagnose debug console timestamp enable
diagnose debug enable

First, show us the "Detail" view of the VPN event log. Otherwise, no one can know what is about.

Toshi

Here's the KB for Understanding VPN related logs:
https://docs.fortinet.com/document/fortigate/7.6.0/administration-guide/834425/understanding-vpn-related-logs