Probably because that version is only in the Unstable branch:
$ mbn info plasma-desktop -q
Branch : archlinux
Name : plasma-desktop
Version : 6.6.2-1
Repository : extra
Build Date : Tue 03 Mar 2026 23:26:01
Packager : Antonio Rojas <arojas@archlinux.org>
Branch : unstable
Name : plasma-desktop
Version : 6.6.2-1
Repository : extra
Build Date : Tue 03 Mar 2026 23:26:01
Packager : Antonio Rojas <arojas@archlinux.org>
Branch : testing
Name : plasma-desktop
Version : 6.5.6-1
Repository : extra
Build Date : Thu 12 Mar 2026 05:44:23
Packager : Philip Mueller <philm@manjaro.org>
Branch : stable
Name : plasma-desktop
Version : 6.5.5-1
Repository : extra
Build Date : Tue 13 Jan 2026 22:11:15
Packager : Tomaz Canabrava <tcanabrava@archlinux.org>
mbn info plasma-desktop -q | grep -Ev 'Name|Repository|Packager'
Branch : archlinux
Version : 6.6.3-2
Build Date : Sat 28 Mar 2026 23:48:58
Branch : unstable
Version : 6.6.3-2
Build Date : Sat 28 Mar 2026 23:48:58
Branch : testing
Version : 6.6.3-2
Build Date : Sat 28 Mar 2026 23:48:58
Branch : stable
Version : 6.5.6-1.1
Build Date : Tue 31 Mar 2026 14:19:08
@pp2222 Try force refreshing the pacman databases when you do the update:
sudo pacman -Syyu
You can also double-check which branch you are on with the following command:
It is important do force the download of metadata after switching branch.
The reason is the timestamp of the metadata.
If the timestamp of your current metadata in /var/lib/pacman/sync is equal to or newer than the timestamp of the server - the metadata will not be fetched - that is how the pacman API provided by libalpm work.
So after a change in mirror list - whether that is caused by change of branch or done automagically using the pamac-mirrorlist.timer - it is recommended to use -Syyu to force the refresh of metadata.
If using pamac - the equivalent is --force-refresh