If you are facing some issues in notifications MiUI7, please try the following steps, which will solve your issue.
Enable "Floating Notification" and "Lock Screen Notification"
Step 1: Tap on "Settings"
Step 2: Select "Installed apps"
Step 3: Scroll down and Select Skooly.
Step 4: Tap on "Show Notifications".
Step 5: Swipe right to Enable 'Floating notifications'
Step 6: Swipe right to Enable "Lock Screen Notifications"
Step 7 Press back to save your settings. Under 'Show Notifications', now you should see 'Badges, Floating notifications and Lock Screen'
Allow Background Network
Step 1: Open your Phone Settings
Step 2: Select 'Additional Settings'
Step 3: Select 'Battery'
Step 4: Open 'Magage apps battery usage'
Step 5: Select 'Choose apps'
Step 6: Open Skooly
Step 7: Select 'Custom'
Step 8: Under 'Background Network' Select 'Stay Connected'.