You will probably need more information. Ask away. This is what happens on my system. My initial reaction is to reinstall the whole system, but then, wasn’t I promised that I only ever had to install once?
$ sudo pacman -Syu [sudo] password for wayne: :: Synchronizing package databases... antergos is up to date 0.0 B 0.00B/s 00:00 [----------------------] 0% core is up to date extra is up to date community is up to date multilib is up to date :: Starting full system upgrade... resolving dependencies... looking for conflicting packages... error: failed to prepare transaction (could not satisfy dependencies) :: gnome-settings-daemon-redshift: installing gnome-desktop (1:3.24.1-1) breaks dependency 'gnome-desktop<1:3.24'