>>1214501sorry about the ugly picture with flash & dirty derailleur :D
Look inside your derailleur. When you've shifted it to that position, is the limit screw touching the body of the derailleur so that it can't physically move further? If it is like in my picture, you need to screw the limit screw out so that it allows movement further.
If there's still room between the limiter screw and the derailleur body, you just need more cable tension. The 5800/6800/9000 generation front derailleurs need a LOT of cable tension to function properly. Do you have an inline barrel adjuster for the cable tension? If you're not getting enough tension with it, first release tension from the inline barrel adjuster, then release the cable, pull it hard with pliers so you get it initially very tight already and then screw it back in the derailleur and then add tension from the barrel adjuster as required.
