“wdphotos apk”? Uh where did you get that APK? WD Photos I believe had been End of Life for a while now. The only currently supported Android app for the My Cloud is My Cloud for Android which can be found in the Play Store.
Currently the only official WD supported methods of remote access to a My Cloud is MyCloud.com, the WD My Cloud app for iOS and Android, or the insecure FTP access option.
Edit to add: The official WD notice of retiring of the WD Photos Android app.
Software Notice - WD Photos Being Retired 5/9/2017
https://community.wd.com/t/software-notice-wd-photos-being-retired-5-9-2017/185596
