This article describes how to resolve this issue by enabling 'Case Sensitivity' in a prompt.
- Launch Management Portal
- Go to Application Builder
- Select the correct application/IVR
- In the application/IVR, select the problematic Play Prompt block
- In the Play Prompt block, click on the Prompt link
- You should see the "Characters" in the first drop down, in that setting ensure that "Case Sensitive" setting is set to 'Yes'