Alfine 11/Versa-11 user here.
If you don’t have the instructions, you’re not missing much – they’re p!ss poor! Better off following the cabling instructions with the hub (IIRC – been several months since I set mine up…)
If the shifter is in 6th and the yellow dots are lining up, either..
– You have a cabling issue, per Al’s comment (most likely – smooth cabling is an absolute must)
– There is something wrong with the hub (mine ran like a bag of nails for a few hundred miles, but has been rock-solid since…. unlike some on here unfortunately)
– There is something wrong with the cassette joint
EDIT: Also check that cable is following the groove in the cassette joint as you go through the gears and is not outside the slot – it will not index as the cable pull between gears will change (….done this…..), also if it’s in a Pompetamine frame and the hub is right forward in the slot, the cassette joint may catch the weld on the end of the chainstay in certain gears (….and this….) just cut a bit of a lump off the cassette joint that you put your thumb on to detension the system, and also make sure you’ve put the cable stop nut into the cassette joint the right way round, so the cable isn’t wrapped over the top (hard to explain, but I did this as well the first time….. 😳