Check engine light

I have a 1998 Jeep Cherokee. The check engine light keeps coming on and it says there is a Gross Leak. We checked all the vacuum lines and can’t find any leaks or disconnected lines. I recently had to rebuild the engine due to blown head gasket and cylinder damage. Help! Can’t seem to figure what is causing it.

Look in these areas. It means there’s a problem in Fuel Evaporation Emission System. You do have the gas cap installed?