Hey! I had the same issue with why facebook keeps logging me out after i closed the app. Turns out, it was my browser settings. If you're using Chrome, go to Settings > Privacy and Security > Cookies and Site Data. Make sure "Clear cookies and site data when you close all windows" is turned OFF.
Also, check if you have any extensions like cookie cleaners or privacy tools that might be messing with it. Hope this helps!
Also, check if you have any extensions like cookie cleaners or privacy tools that might be messing with it. Hope this helps!