When you download the app, it asks you to give permissions. If you have not given all or some of these permissions, you cannot use all features of the app.
If you change your mind you can resolve this by taking one of the followings steps:
1. Go to the settings of your phone or iPad and look up Translator and make sure that you click on allowing translator to access the camera and/or microphone.
2. Delete Translator from your device, reboot your phone, go to the online app store and download Microsoft Translator again. When you then open the app for the first time it will ask you for permissions.