@clockpops A few things you can try if you still wish to use Facebook 🙂. I know you say you have checked settings but ensure all the relevant categories are toggled on. otherwise try Resetting the Network connections firstly -Settings-General Management-Reset-Reset All Settings.
Sometimes can be conflict with 3rd party apps/theemes, if ok in safe Mode would pinpoint recent third Party apps which have been installed. https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/
If no resolution try clearing the cache partition by following steps:
1. Turn off the device.
2. Connect To Computer , other Device or TV USB, Press and hold the Volume Up key and then press and hold the Power key
3. When the Android logo displays, release both keys.
4. Wait until the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.
@cloclopops: While I understand that you may have already checked this, please make sure to check all notification categories for Facebook to ensure that the relevant ones are toggled on. To do so, head to Settings > Apps > Facebook > Notifications > Notification categories > Toggle all options on from here to your preference.
I also recommend heading to Settings > Battery > Background usage limits, and make sure that Facebook is not listed in the Sleeping or Deep sleeping apps categories, as this can restrict notifications.
