Teller, my Mom has the very same issue almost every time she tries to enter the park. We have annual passes and its a hassle every time. She scans her finger and it doesn't work. They have her do it again, still no go. They ask her if she is using the same finger and to try a different one. After having her try 2-3 times, they raise their arm to call over a Supervisor. Supervisor asks if she's certain she is using the same finger. She says yes. Then supervisor has her reset her fingerprint. At this point they also take her picture or look for her picture in the system. This whole process takes 3-4 minutes which is forever if you are in line behind her. She now tell the first cast member to call a supervisor because her finger prints can't be read. She also tells them there is a photo of her on file. It doesn't matter. They ignore her and go through all the steps every time. It is so frustrating for her!!!!
I always enter the park in front of her and meet her in the first gift shop (there is one in every park). At least, that keeps my blood pressure down.