RHEL 7.5 wakes up from sleep with blank screen

I have RHEL desktop 7.5 installed on my HP Probook 450. when i close the lid on my laptop , the OS goes to sleep, but when i open the lid and press the power button, only the keyboard LED's and power button light up, but the Screen remains black.

i have to hard reboot (press power button for 5 Seconds). please help. what could be the issue.