Hello,

I came across same issue, but when i actually fixed the same the thread was locked for replies. DSo here is the solution whoever is looking for one.

1. First temporarily connect cable to your main router and wds router.
2. Go to your Main router settings -> Advanced -> uncheck Smart connect (if checked)
3. Then name your 5ghz a name other than your 2.4ghz network
4. Here under mode select non ax option, i think its because of this the Archer A7 is not able to find as A7 is AC router and my m ain router is AX.
5. Once that is done change channel to 36, then log into your WDS router and check if you are able to find the 5ghz network.
6. By doing so you should find the network, set it up in WDS router.
7. Then revert the changes to the main router, i.e. channel to auto and mode to with AX option.

This steps will get you going.