It took a while to load for me as well, but it still came up. The link was posted on another fairly popular site and thats probably pushed the traffic too high for them.It hasn't loaded for me, either.
Reading the review paper, this doesn't come across as a very convincing measure.
It's limited to headlines only, and the ability to discern fake headlines.
That's a very small part of understanding misinformation, and one that is probably even more limited than it once was as news is consumed so differently than in "newspaper style format".
The fact they found that if someone does a training on disinformation (the Bad news game) they get better at spotting fake headlines but also classify more real headlines as fake.
I think this may have some use as a general population measure in some ways, but is probably very bad at measuring individual susceptibility to fake news.
Sure, its a limited study with only 20 questions based real and generated headlines. Its still worth checking out, if it works.