I believe Bisbonian is on the mark for a solution to your problem. The User Code prompt automatically comes up when your ignition key, which should have an electronic chip embedded in it's head, is defective, not programmed, or is a standard key without a chip. This thread should be of some help for you to program the keys you have for the bike:
https://www.guzzitech.com/forums/threads/user-code-screw-up.17453/
A couple things to make note of:
1. The User Code can be changed to any 5 digit number you choose, as per instructions in the owner's manual.
2. The Service Code is a different number, should be 34534 for your bike, that must be entered for the SERVICE menu option, which will get you to the Change Keys option. This code is not changeable, as far as I know.
3. When performing the Change Keys procedure, be sure to program all of your keys, up to the limit of 4. In my past experience, having only one key programmed will trigger the mysterious Red Triangle indicator on the speedo/tach display.