I am using Samsung Galaxy A9 (2018). Today morning my phone received a security patch update and after the installation, my phone is not switching on. rather my phone is stuck at the "SAMSUNG" logo screen. Kindly help me.
If the device did not fully complete it's update, you're going to need a software recovery. To get a software recovery done to the phone you two official options. You can contact 1-800-SAMSUNG or visit https://www.samsung.com/us/support/service/locations/ and see if a samsung authorized repair location near you is open and will perform the software recovery for you.