It is possible to do that. You can refer to this link to set up: http://www.tp-link.com/en/faq-1270.html

What's the model number of your router? Can you connect other wireless clients to the same wifi? What's the error message on the phone when trying to connect?

You may try to locate the problem on the devices first. Is it only 1 or 2 of them? Or all 3 of them? If only 1 or 2, I think it's possible that the device you have is faulty or something. While if it...

Are you at home when trying to access it? It should be faster in the local network, while for remote access, it would be slower depending on your internet speed.

Is that Android 7.1.1 a smart phone or a tablet? For tablets, it's possible that some have compatibility issues.

Thank you for sharing :)