FNB APP

This morning checking the FNB Mobile app is noticed that my chq account is in overdraft. I know for a fact that this account is not in overdraft as I check my balances daily. If I log onto the FNB Web portal and check the balances I am not in overdraft. Please explain this to me how does the app not communicate with the web portal. If there was technical issues why was I not informed. This is not on. This is also not the first time something like this happend.