Be sure you have not set the schedule where it is outside the time for the guest network. Also be sure to page to the bottom of the screen and click save. Try rebooting the router as some changes require a reboot. Also try encryption auto. Be sure the SSID (network name) is not used somewhere else. And try deleting (forget) the network name on your PC and restart it.

@ArcherC8 

I disbaled the scheduled time, There is just one wifi in the area because its and isolated area. i clicked save but didnt reboot, but now i did but still it wont coonect. 

@Cooper82 

 

I looked at your Manual (https://www.tp-link.com/us/user-guides/TL-WR840N_V6.2/chapter-4-configure-the-router-in-standard-wireless-router-mode#ug-sub-title-7) and it shows the Encryption as 'Auto'. See if that would work if changed?

 

Although this FAQ isn't for your router, it to says use the Default, https://www.tp-link.com/us/support/faq/1561/

Thank you all, i figured it out. its the mac filter that is doing that nonense, i have to add guests mac in select the host as guest.