@Nahian the US version of Archer C6 supports these channels. On the old TP-Link models you could change the region and get around it, but on the new ones you can't. You can try installing US firmware but it's risky as model specifically says EU.

@netcrypt9119  I tried to install the latest US firmware but the router didn't allow to do it!

Then I tried to downgrade to the oldest firmware of EU version, but it could not be installed :( 

My Apple devices can connect fine to the router, but none of my Samsung devices will connect to the 5Ghz band. Since I have a dual band extender (RE200), connection is stable enough so doesn't really matter. The extender uses the 5Ghz band when available to communicate with the router and the devices connect to the extender via both bands.

@Ayman_Tanvir you can try TFTP recovery maybe, but do this at your own risk and you may lose warranty

https://community.tp-link.com/en/home/forum/topic/81462?page=1

@Ayman_Tanvir I just wonder why TP link is selling that version (C6 EU) which is not actually fit for BD region. Beacuse most of the BD devices works with band 4. When I bought this frim Star Tech, they also told that both band will work fine with my mobile devices. But when I configured, it didn't. Its really poor move for TP-Link.

@Zhelper thank you so much, worked for my redmi note 8

@Nahian turn ur phone to airplane mode, switch off wifi and then switch on again you will find the 5G connection.