A340 MCDU Fuel Time No Optimal

[Double Asymmetric]

Hello,

a quick question, can anyone explain how the MCDU on the A340 can arrive at this message? I am new to glass cockpits, and have been told by some it simply means "it's not worth going any higher...probably due higher winds in the system." However, I very recently flew with a captain who went into a detailed answer of a sliding range around the manually inputted step climb position, and if this message comes up it means the box can't find a better position to step climb than the manually inputted one.
Is there anyone who can enlighten me? Sorry if this is a basic question...I do want to understand what my aircraft is telling me!!!

DA

[Back Seat Driver]

FMGS Pilot’s Guide

MULTI PHASE RELATED PROCEDURES
OTHER FUNCTIONS
Optimum step
Rules
– The OPT STEP is only computed by the FM if data required for the prediction computation are
inserted : F-PLN, CRZ FL, CI, GW, CG at least
– The search of the OPT STEP begins 20 NM beyond T/C before Cruise, or ahead of aircraft position
– The search of the OPT STEP ends 20 NM before the next STEP POINT or 300 NM before the TOD
– Only one OPT STEP is computed at a time.