Make sure the cable wasn't kept in a humid environment or got slightly wet,same for the phone's usb C port. I had that many times and after drying it with the hairdyer(dont use maximum heat ) ,it started to charge.
In your case,because the phone is out of charge,try like somebody suggested to use a different cable/charger or PC ,if the phone is completely discharge, it will take a minute in order the battery symbol to appear on your screen. leave the phone in charge for 2,3 min and do the following:
Turn off the device .Press and hold the Volume Up key and the Bixby or Power key.Once the Android Recovery screen comes up, release the buttons.Use the Volume Down button until you are highlighting ‘Wipe cache partition.’Press the Power button to select ‘Wipe cache partition.’Use Volume Down to highlight Yes.Press the Power button to confirm the action to clear the cache.Wait for a second as the system wipes the cache. Use volume keys to navigate up and down the menu and power button to select what action you want to perform.
In your case ,i suggest you to select delete all date,this will reset the phone to factory settings, then you start fresh. It will take good 10min for the phone to reset,all you'll see is Samsung logo or blank screen from time to time, wait until the phone reset,then start fresh
