Hi there and welcome
First, to be sure, did you perform the installation as following?
Turn the selector dial to 1 (the factory setting) on the Keyboard
Press and hold down the “pc” connect button for 3 seconds.
Click Settings in the upper-right corner of the display.
Click Change PC Settings.
Click PC and Devices and select Bluetooth.
Select Logitech Keyboard K480 and follow the onscreen instructions to complete the pairing.
Then wait 20 minutes for the install and updates to complete and then try to use the keyboard
Let me know the results please