First you need to know that Archer C7 has 6 antennas in which 3 are of 2.4GHz and 3 are of 5GHz,2.4GHz antennas are internal antenna and 5GHz antenna and the external antenna and the 5GHz antennas...

I think you should reset the router and reconfigure it again and update the WA5210G to the latest firmware available. And if your budget is that much to should replace the TL-ANT2409A with...

I am not able to understand what you want to say.

Then check from your client that your are connected to the AP and are you able to access the AP GUI.Then go to your AP Settings. Before making these settings reset your both CPE510.

OK i corrected it now. Select your region to United Kingdom And remove tick from DFS option. Now do the setting in you second AP as client Note if you enable MAXtream in your AP, only TP-LINK CPE510...

Just watch the Pictures and set the setting as in the image. This is for your home AP. Now the Second CPE510 as Client mode at your stable.