Initially I got the failed to sync AUR. But after trying over a period of time this issue was resolved.
However, I then got the error below when trying rebuild Deadbeef 1.9.4 → 1.9.5
The solution was to install pkgconf from the official repository.
configure: error: in `/var/tmp/pamac-build-yt/deadbeef/src/deadbeef-1.9.5': configure: error: The pkg-config script could not be found or is too old. Make sure it is in your PATH or set the PKG_CONFIG environment variable to the full path to pkg-config. Alternatively, you may set the environment variables JANSSON_CFLAGS and JANSSON_LIBS to avoid the need to call pkg-config. See the pkg-config man page for more details. To get pkg-config, see <http://pkg-config.freedesktop.org/>. See `config.log' for more details ==> ERROR: A failure occurred in build(). Aborting...