Zwift cog stuck without change

Hello, during the training session, my cog are stuck on the left box on top, where you can see the zone and training specifics, and I can’t switch the gears (when I tried to click + or - buttons I can only change the % of watt)

Thanks

If you are doing a workout where there is a power target, then what you describe is normal.

Thank Paul, just to be sure that I understood correctly, during the workout I can’t switch my gear? Look like weird

If you are in ERG mode, resistance is controlled by the trainer. You just pedal and it adjusts so you will meet the power target at whatever cadence you are doing. If you are doing a workout without ERG mode, you would use the +/- buttons to adjust resistance. If this is not how you want to do a workout then you can do your training in a free ride instead.