Can't grant access to photos on iPhone 5s

I have an iPhone 5s with iOS 9.3.5. I am trying to use a SanDisk iXpand external drive to back up photos from the phone. I am using the iXpand Drive app.

When I insert the drive and open the app, the app says: “Cannot access photo library. Please enable access to your photo library in the Settings app.”

When I open Settings, Photos is not an option in the iXpand Drive setting (microphone, camera and Notifications are listed). When I go to Privacy and select Photos (where Apps that have requested access photos are supposed be listed) nothing is listed.

Any idea how I can grant this app access to my photos? 

Thanks!

it should be in the privacy settings for photos. you may have accidentally denied permission to access the photos when you first installed the app. If you do not see the iXpand drive app in the privacy settings for photos try uninstalling the app and reinstall fresh. It should ask to access your photos during the app setup. Grant it permission to access your photos. 

Thanks drlucky, that worked! I don’t know why I didn’t think to delete and reinstall the app. Thanks again!