Symptoms

The promo code for the mobile application on iOS platform cannot be activated. When the About button is tapped and held, the window for entering the promo code does not appear. 

Solution

Open the application, go to Settings, and make sure that there is no checkmark/expiration date or mark Purchased opposite the Premium Account option.

If so, close all the applications running in the background, install the available updates for the operating system of the mobile device, reboot the phone, and try again.

If there is a checkmark/expiration date or mark Purchased opposite the Premium Account option, wait for the current subscription to expire and activate the promo code then. 

Additional information

FineReader PDF for Mobile promo code activation

TextGrabber promo code activation

Promo code activation in BCR for iOS