@olangbrg 

Hi, thank you very much for your patience.

Could you please help me check the IP address and gateway when you are connected to the guest Wi-Fi?

If only leaving the main Deco, would the guest network have internet service?

Since the main network and guest network are separated by VLAN, could you please help me draw a picture of your network structure?

--If there is a management switch, please also check if any VLAN tags enabled on the switch;

Thanks a lot and wait for your reply.

@olangbrg 

Hi, thanks for your reply.

How about your network map, like:

                                                /wireless----2^nd Deco

ISP router—main Deco M5(AP mode)

                                               \  wireless-----3^rd Deco   

If not like the above structure, how are the other two satellite Decos are connected, wireless backhaul or Ethernet backhaul, and would there be any switches?

and currently, the smartphone would connect to the guest Wi-Fi but no internet, and the laptop did not connect at all, right?

If we cancel the security type on the guest Wi-Fi and make it an open network, could the laptop get connected?

Have you checked if only the main Deco left, would the same issue still here?

Later we would like to follow up on your case by email and please have a check of your email box later.

Thank you very much and wait for your reply.

@olangbrg 

Thanks for your quick reply.

Can I also have the model number of your ISP router as well as the unmanaged switch?

By the way, could the laptop be able to connect to the guest Wi-Fi when it has no security?

How about temporarily turning off the Deco 2+3, would the guest network start working?

Thank you very much and wait for your reply.

update:

After checking of the senior engineers, there would be another possibility: the DNS server might be mistaken as one of the host network clients and would be blocked to communicate with the guest network devices;

So could you please check the DNS server on your network to see what it is?

and if possible, please change it to be 8.8.8.8/8.8.4.4 to have a look?