Router have connectivity but client doesn't

[iTheMask]

I have RT-AX3000 running Asus Merlin 3004.388.5 which was working fine till today, now all my devices cannot connect to the internet via IPv4 (somehow IPv6 is working)

• I haven't changed any configurations for the past month
• Last upgrade was more than one month (from 3004.388.4)
• Router is assigned IPv4/IPv6 through PPPoE
• I've disabled IPv6 and restarted, same issue persisted
• Router can ping internet IPv4 just fine, while other WiFi/Ethernet clients can't
• DDNS is updated successfully
• I can connect to the router VPN server from different network (but no Internet connectivity for the client)
• I noticed that the nat-start script is not starting
• I've restarted the router multiple times

Any help tracing this issue is appreciated

 

[iTheMask]

I've performed factory reset on the router which seems to have resolve the issue.

Need to redo all the configurations now