Push Notification of Facebook Official App Not Working

I use Samsung Galaxy Note 4 SM-N910C that is rooted and running official marshmallow. All was going well for 6-7 months. But suddenly I am not getting push notification from the facebook app for the last month. I have tried clearing data of the app, turning off platform, uninstalling greenify. Butnothing worked. What to do now? Please help. :(

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