Block device doesn't actually mount and no errors are reported

You probably have (or had) an /etc/fstab entry for the same mountpoint but a different device. Due to a badly implemented feature in the systemd manager (which was supposed to remove mounts in case the device disappears), it automatically removes mounts whenever the device doesn't exist – and sometimes prioritizes the stale information from /etc/fstab over the "live" mount information. This sometimes results in new mounts being immediately unmounted.

• Check journalctl -n 100 to see if this is the problem.

• Remove the entry from /etc/fstab, then run systemctl daemon-reload before mounting the device again.

• Try to mount the device at a different location.