@Shiv741 Can you post that screenshot:

@Shanky2201 When you making the first screenshot, can you click on the Archer C6 icon to visualize the ethernet status and re-post it: Are you aware if your ISP is using a MAC address protection ?

@Shanky2201 It's highly unlikely you got two faulty devices in a row. Describe your topology/network setup. How do you receive your internet service ? (PPPoE, dynamic IP, any ISP modem / router...

Try the wireless security settings from my first post, reboot the device so all your devices can re-connect and test again. This way we can exclude the possibility of wireless settings issue.

@Shanky2201 The one that the device originally came with.

@Shanky2201 TP-Link are working on a new official FW version. In your case it may turns out to be just a faulty unit. You can try one more thing to be sure that you've covered everything. Revert back...