Notifications for 3rd Party messenger apps dissapearing after 1 second. Mate 10 pro.

[Android Central Question]

So this past month ive had this issue where my notifications for apps like FB Messenger and whatsapp will just flash up for 1 second then dissapear, so if im not on my phone i wont know if i have a message. I tried resetting my app preferences and this worked for 1 day then i started having the issue again. Its really driving me mad at the moment! Please help