TryAPL API request loads endlessly without returning

I am following the instructions in the APL Wiki but I am not getting anything back. The examples are in a language which I am not familiar with, but I think I understand enough to see that my answer isn't there.

I am using Python and the bare-bones script below doesn't work:

import requestsprint(requests.post("https://tryapl.org/Exec", json=[0, 0, 0, "2 + 2"])

It loads endlessly without returning any error message. According to the APL Wiki I shouldn't need to set the first three values in the POST request to anything for it to work with such a simple expression.