@Jimjimjim AP mode did it. I had to restart several times, and hard reset each chromecast devices.

@Jimjimjim callend TP Link. They suggest to change top access point only, instead of router mode. Well.. ok .Let's try it. Before getting a prooer messh system. And then by TP Link,

@TP-Link U can have both. Bangladesh or any country. https://community.tp-link.com/en/home/forum/topic/154561

Can't add a Google Home, Home mini or Chromecast audio. I see them but when i try to confingure, on the first steop tryinf to connect to the device, it alway says Cant establish communcication Deco...