FORTIGATE TROUBLESHOOTING IPS ENGINE

First  execute:

#diag test application ipsmonitor

IPS Engine Test Usage:
1: Display IPS engine information
2: Toggle IPS engine enable/disable status
3: Display restart log
4: Clear restart log
5: Toggle bypass status
6: Submit attack characteristics now
97: Start all IPS engines
98: Stop all IPS engines
99: Restart all IPS engines and monitor

After list those commands for choose some option execute the command like that:

sample:
diag test application ipsmonitor 99