Formulas not unlocking after a purchase may happen when your network or iTunes is slow. When you make a purchase, you're asked for your iTunes password and when the purchase completes you will see a “Thank You” message. This message automatically goes away after a second and the formulas should be unlocked. If you did not receive the “Thank You” message you can tell the app to check again, which you do by pressing “Restore Purchases”. This button can be reached by opening a locked formula, tapping "Unlock" and scrolling to the bottom of the list of unlock options.

If “Restore Purchases” does not work you may try again later or it may be that your purchase did not actually complete. In this case you can select the same unlock option again and purchase again. If indeed your purchase did already go through, iTunes will not charge you again and you will see a message explaining that “you have already purchased this item, do you want to download it again?”. Confirm this dialog and wait for the “Thank You” message to appear, then your formulas should unlock.

Note that “Restore Purchases” will only work if you have previously unlocked MedCalX, purchases from MedCalc cannot be restored. For that you must first obtain a free unlock.