Can refer to:
https://community.fortinet.com/t5/Support-Forum/GRE-Tunel-not-working-after-7-4-1-gt-7-4-3/td-p/298665/page/3https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-GRE-traffic-stops-working-after-a-firmware/ta-p/308279
Thank you, Kaskipl. Are both ends of GRE site FGT-VM? If you could share
your configuration file, it would be conducive for us to reproduce the
issue. My email is: kmliu@fortinet.com