This is related to the device you are using and isn't an issue with the app. Make sure battery optimisations for the app are disabled.
Please go to this website and run through the steps to keep apps alive for your device: https://dontkillmyapp.com
As stated in the app, this is not possible. The custom status bar overlays the original status bar, but there is no way to hide the original status bar. There is no fix for this.
If you are using MIUI, make sure the "Display pop-up while in background" permission is granted. You can find this by opening Super Status Bar in the app list in the Settings app.
For some reason Google hasn't synced your purchase yet.
It usually fixes itself after you update your apps in the Play Store by tapping the 'refresh' button in 'My apps & games'.
Try Google Opinion Rewards. It allows you to earn Play Store credit which you can spend on apps.
If a toast message is appearing saying that an app is blocking the dialog, make sure you disable the Draw Overlay permissions for all apps before enabling the Accessibility Service.
If you cant see the app in the list, tap 'More downloaded services' or similar.
Otherwise, try restarting your device.
Restarting your device should fix this. If it doesn't, try reinstalling the app.
Long press the notification to hide it
Unfortunately Android does not let apps change the auto brightness level all of the time. You can try enabling the "Allow changing auto brightness" option in Extras, but this may not work due to Android limitations.