Even GCU mentions an inactive link for Agreement To Serve that the student must sign.
https://www.gcu.edu/admissions/tuition-and-financing/scholarships-grants.phpr
“Sign an Agreement to Serve and complete entrance counseling each year that you receive a grant
Complete these forms at the Department of Education’s website: teach-ats.ed.gov”
Googling teach ATS brings up https://studentloans.gov/myDirectLoan/launchTeach.action
Did your daughter sign?
Then there may also be a problem with federal government accepting her if the federal government has changed its rules.
Furthermore, GCU has this requirement:
"Counseling
You are required to complete entrance counseling through the Department of Education site each year that you accept a TEACH Grant. You will also be required to attend exit counseling when you graduate or leave school.
Documentation
Within 120 days of completing your program or ceasing enrollment in your program, you must notify the U.S. Department of Education that you are fulfilling (or plan to fulfill) the terms and conditions of your service agreement. You must document your teaching service annually; the chief administrative officer at the school where you teach must certify your documentation."
It doesn’t seem right to me that GCU and the federal government may have processed your daughter 's TEACH grant, yet, now say she is ineligible.