The old domain we used to host #ArchLinuxARM for #PinePhone / #PineTab2 has expired.
Open /etc/pacman.conf in vim, nano or any text editor and change "p64.arikawa-hi.me" domain to "archmobile.mirror.danctnix.org"
You can also use sed to do this in one line:
sudo sed -i 's/p64\.arikawa-hi\.me/archmobile\.mirror\.danctnix\.org/g' /etc/pacman.conf