Hi,
I understand that access from 192.168.1.0/24 to 192.168.100.0/24 is fine however otherway access is not working.
Please check to which zone these ports belong to, on each firewall. And then check your have security policies on both the devices to allow the traffic in both directions. Each device may have at least 2 security policy to allow the communication in either direction.
Thanks,
Vikas