horrible arch issues

When i say i have wifi issues, I mean I couldn't install a DE (but i specifically wanted KDE Plasma) both through archinstall and the manual way. One time, it worked, but when i rebooted, it broke. It can't connect to the mirror sites. My wifi card works with Linux Mint, which is my current distro on my T420. It also worked well with Windows 7. I also had the same problems when I tried to install Debian. My wifi card is the Intel Centrino Advanced-N 6205. If anyone has any ideas why this is happening, please tell me.