Hello @Dedes
Do you mean there is an internet IP address on the router WAN/Internet page but there is no internet access when the devices connect to the router? Be sure you have internet access when connecting a computer directly to the smart rocket sim (I guess you are referring to a modem?). If the internet does work when connecting to the modem directly, please do a simple test on the C64 router:
Go to Advanced > System > Diagnostics, please ping 8.8.8.8 and www.google.com, then check if the ping result is normal. If you can ping 8.8.8.8 but not www.google.com, please go to Network > Internet page, choose Advanced Settings, manually change the DNS server to 8.8.8.8, then save and reboot the router to determine if the internet works.
It's also suggested to follow the guide to do further troubleshooting:
What should I do if I cannot access the internet through Wi-Fi router?