Because our building is too large to have wifi service from only one router, we operate two tp-link Archer C9 routers: a main router called "Locked1" and a second C9 called "Locked2" which is configured as a Wireless Access Point (WAP).

I used Advanced -> Guest Network to set up wireless networks for guests (2.4ghz and 5ghz) on each router.

All four guest networks have the same password.
All four guest SSIDs are broadcasting, and guests can log in any of them.

When they use either of the Guest SSIDs on the "Locked1" router, they have internet access.

However, when they use either of the Guest SSIDs on Locked2, their phones and ipad show the words "no internet connection" next to the network name. (I have tested this with my own laptop and iphone, and i experience the same problem.)

Locked1 specifications:

• Archer C9 v.3.0 with firmware 1.3.1 Build 20171215 rel.35219
• This is the main router for the building. It does DHCP and wireless access.
• It is connected to the cablemodem using its WAN port.
• This unit broadcasts four SSIDs, called:
  • Locked1_24ghz
  • Locked1_5ghz
  • Guest1_24ghz
  • Guest1_5ghz
• All four SSIDs are working correctly and providing internet access.

Locked2 specifications:

• Archer C9 v.4.0 with firmware 1.0.1 Build 20171219
• This is the secondary unit. It is located at the other end of the building in order to provide wifi coverage to that end of the building.
• This router serves as a WAP only. DHCP is turned off.
• Locked2 connects to Locked1 using a cat-5 cable. This cable goes from one of the four LAN ports on Locked1 to one of the four LAN ports on Locked2. (The WAN port of Locked2 is not used.)
• This unit broadcasts four SSIDs, called:
  • Locked2_24ghz   [working]
  • Locked2_5ghz     [working]
  • Guest2_24ghz     [no internet]
  • Guest2_5ghz       [no internet]
• The two Locked2 SSIDs are working correctly and providing internet access.
• The two Guest2 SSIDs are broadcasting, and devices can connect to them. However the devices that connect to Guest2_24ghz and Guets2_5ghz have no internet access.

So guests who connect to either Guest SSID of Locked1 have internet access, but guests who connect to either of the Guest SSIDs on Locked2 have no internet access at all. This is creating a big problem! 

I need help determining what changes I need to make to the configuration of Locked2 in order to provide internet access to the guests at that end of the building.

Note: I have viewed the tp-link YouTube video "How to turn a router into an Access Point" and followed the instructions ( Click for YouTube Video )