Make Sure you are Running Darkmatter in Full Resolution (Your desktop/laptop's Screen Resolution)
Although, as I've seen. If you Install Pubg in any mod os of phoenix.. The Game Helper Automatically Provides Default Keymapping.
The Only Fix Coming to my Mind yet is -
1st . Re-installing Pubg From Official Sources . (Google Play Store)
2nd - Try Checking Game Helper Application After You Install Pubgm. There Will be an Icon To Turn on & off Keymapping.