If the Fax button is dimmed, it is most likely that in-app purchases were restricted on your device.
How to allow in-app purchases
- Open the iOS Settings of your device > scroll down to Screen Time.
- Tap Content & Privacy Restrictions and enable the toggle.
- Tap iTunes & App Store Purchases > In-app Purchases > Allow.
Note: You need to log in to the Apple ID that was used for the Scanner Pro purchase. This is essential for in-app purchases like Fax.