When I try this in an incognito window with wifi turned off it doesn't seem to work. I see some invalid date error messages.
It's only when you fill out the "Current situation" inputs that the request to the API fires to run the calculations and return the results - I suspect the case here may be that the request hasn't been fired yet as the inputs haven't been fully filled?
I'll be working to make this user journey more clear in any case
Why use an API? seems like that raises a lot of security/privacy issues and these calculations are simple enough to do locally, no?