The Nokia Pro Camera app has been updated and is now called Nokia Camera. If you have Nokia Pro Camera installed, you will get an update notification that replaces it with Nokia Camera on your device.
In case you updated several apps at once, it's possible that the Nokia Camera update slipped by without you noticing. Once the update has been done, Nokia Pro Camera is permanently replaced by Nokia Camera. Nokia Camera supersedes Nokia Pro Camera and includes all the old features as well as lots of new ones.