If you have an issue with gpg verification of packages the instructions are slightly different to recover as the signing keys are different:

pacman-key --init
pacman-key --populate archlinuxarm

This is if you get errors like:

error: mutt: signature from "Arch Linux ARM Build System <builder@archlinuxarm.org>" is unknown trust
:: File /var/cache/pacman/pkg/mutt-1.10.0-1-aarch64.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] y
error: failed to commit transaction (invalid or corrupted package (PGP signature))
Errors occurred, no packages were upgraded.