You need to do 2 things.
- Reach test coordinator with documents.
Make sure testing center and staff are available for accommodation (room is available and supervising adult too.) - Send your child with copy of accommodation letter by the College Board in hands and instruction to go over accommodations with room attendant before the test.
We had situation when on AP exam room attendant was not aware about most recent accommodations and refused them. (It was opportunity to write in booklet for multiple choice…) We were offered later to retake but my child refused…