IPSec Connection Between Static IP Fortigate Firewall and Dynamic IP AirLink LX60

Has anyone successfully setup an ipsec vpn tunnel between a fortigate Firewall with a public static IP address and Sierra Airlink LX60. I have tried various configurations with no success. Can’t even get past phase one. Getting lots of mixed messages from both vendors. Looking to connect many remote sites to a central fortigate firewall via the Sierra products if I can just find the correct configuration for each device.