Many users were reporting about this issue that they are unable to upgrade the app and get an error code -505. 

Unfortunately, this is due to Google Playstore. 

Currently, we are not sure of exact reasons but here are some steps as suggested by Google to troubleshoot the issue. 

Clear cache and data

  1. Open your device's main Settings app.
  2. Touch Apps or Application manager (depending on your device, this may be different).
  3. Touch Google Play Store > Clear cache > Clear data.
  4. Touch the back arrow Back arrow.
  5. Select Downloads or Download Manager > Clear cache > Clear data.

If the issue still persists, please refer to below link:

Steps to troubleshoot as per Google

Let us know how it goes.