Hello -
Which version of LEAP are you using, and did you begin by creating a new LEAP area (a new model)?
LEAP contains a number of default fuel options that you may select from, including Hydrogen. Could it be that you have inadvertently removed this fuel from the Fuels Database?
Note that you may always create or delete fuels within the Fuels Database. See here for more information:
https://leap.sei.org/help24/Supporting_Screens/Fuels.htm
Taylor