When set two different ONT OT928G with two diffent PC's, each PC cant ping each other even the ONT928G FE port has been set by using native VLAN.
1) MA5680T manual on support website.
2) Try to do some configuration on the equipment.
This is a security features by not enabling each users on ONT can ping to each other by not setting a routing gateway.
1) On MA5680T, set interface vlan 100 by IP: 192.168.0.1/24 and PC1 by IP: 192.168.0.2/24
2) Interface vlan 200 by IP: 192.168.1.1/24 and PC2 by IP:192.168.1.2/24
3) Each PC's has be to set on each respective vlan interface ip as the gateway.
4) now PC1 on OT928G-A can ping to PC2 on OT928G-B