How to fix push notifications in MIUI, To get around MIUI's memory management, you'll have to select autostart for apps that aren't sending push notifications.

Open Settings from the home screen.

Scroll down to the Apps sub-menu.

Select Permissions.

Tap Autostart.

Choose the apps that aren't sending push notifications.

Toggle the slider to ensure the apps always start in the background.

If you don't see a particular app listed in autostart or are still facing issues with notifications, you should disable the built-in battery optimization. Doing so will ensure that the app isn't being restricted by MIUI's memory management.

Open Settings from the home screen.

Scroll down to the bottom of the page.

Select Battery & performance

Tap Choose apps.

Select the app that isn't showing notifications.

Choose No restrictions.