Facebook Messenger Message Notification 🙄

 l have been a customer of Samsung Galaxy M31s for the last eight months, since last two months Facebook Messenger has not received any message notifications, none of other apps has this problem, Message notification is accurate on WhatsApp and other all apps, As well as SMS notification there is no problem, from this l understood that there is no malfunction in the phone, Acces permission has been granted for everything in App store,nothing is denied,only Facebook Messenger has this problem, I removed Cache,then uninstalled Facebook messenger and reinstalled to resolve this issue, Yet this problem could not be solved,l think l can fix this issue through Reboot the phone ? Can anyone suggest a solution to fix this issue ? Please advise !