Is this how you accessed ISFAA? (See directions from Amherst below)
This is how you should access it AFTER you apply to Amherst (when you will have an admission account.):
Applicants for whom the CSS Profile application fee will present a serious financial hardship should submit a request to complete the International Student Financial Aid Application (ISFAA) by logging into their admission account.
https://www.amherst.edu/offices/financialaid/international_students/appleton
ISFAA is not due for Amherst ED applicants until Nov 14. So stop working on that now, you have other apps that need to be done by Nov 1, including Oberlin, Bard, and Reed EA apps.