If you are in Brazil
The Chrome Web store from Brazil has a problem that does not allow to install this app. Please use instead the US Chrome store link (which has the same subscription cost).
If you are using a Google Apps for Education (GAFE) Google ID
The Chrome Web Store doesn’t allow GAFE users to install paid apps even if they have a free trial. IT administrators and/or teachers should sign-up for a plan here.
After you are signed up for the plan, you will received instructions on how to install an education specific version of the Arduino Create Chrome app, a tutorial that explains all this is available here.