@Atul2 You can't downgrade from the current FW release: What you can do is to try to connect the TV to wireless guest network. If that doesn't work as well reset the router to factory defaults and...

@Miraki Archer C6U doesn't support Print Server: Probably using hardware like this one would do the job.

@Atul2 Try these settings:

@dobmarton WR740N is with old green UI. Even if you update to the latest FW release this won't change the old green UI. For restricting internet access on your device you can use Access Control...

@ace543 That's a known issue (the site admin should take care of these changes). Eventually these will be updated on the regional websites as well. Therefor for EU FW releases the most current source...

@makrz You can reset to factory defaults, then re-configure from scratch and see if that will resolve the issue. By the way there's a newer FW release for your router here. (For EU version).