macOS Mojave Bluetooth

I am using a Late 2015 iMac. My LMP Bluetooth Numeric Keypad used to work just fine with my system prior to the upgrade. Somehow it lost the connection. Now when I try to re-connect it to the computer, I am never able to enter in the code. The little box just flashes on my screen for about half a second then goes away, and the Bluetooth System Preferences says "Connection Failed". What is wrong?