No Chat Head Notification When Locked Screen

[alinesku]

Hello
I encounter the following problem:
-my phone is sleeping
-i receive a facebook message through messenger app
-i do not receive any sound or led or vibration
-only when i press the power button and the screen lights up in lock screen mode i receive the sound and vibration notification but no chat heat
-if the phone is in home screen mode everything is fine, i do receive notofications and chat heads because i already set up allwing pop-up notifications
-so, the problem is more than i can find on internet and it is when the phone is on sleep lock screen mode.
Please help me with solving this issue.