In 30-days-of-postman-for-developers, the Day 11 , API link given is not working

I am learning Postman through the 30 days of postman for developers. I have been able to successfully complete the 10 days of it, but the API link given in Day 11 - Monitoring of the tasks is not working.
This is the link given in the exercise.
https://water-ttl.herokuapp.com/hygrometer

But this gives a 503 - Service unavailable error. Could some one help ?

Same thing happening for me.