Rankk is currently in a transition from Python 2 to Python 3. You might have also noticed that only Level 1 and Level 2 challenges are currently accessible there.
That also affects the WeChall linking scripts, which are currently not working. For this reason, the site is still marked as "temporary down
Until those scripts are ported, we will keep the site marked as down until you can use it with WeChall again.
PS: Things are in the process of being fixed