Seems like you did something wrong.
Gcam Service Provider would indeed interfere with Sandboxed Google Play. If you have it installed please delete it.
When we say Sandboxed Google Play we mean all three apps: Play Store, Play Services, and Services Framework.
Please make sure that you have installed all three of them.
For more information please refer to the official documentation:
The way you downloaded your apk is quite unusual.
Yes, there are multiple different official versions of Google Camera designed to work on different hardware.
You might have downloaded and installed the wrong one.
Please use Play Store to download proper Google Camera app which is compatible with your phone.
Hope this helps