Okay, it looks like it's supposed to be twisted on purpose, or rather cabled. Have you done cables before?
Here's where you're going wrong, I think -
"c6f (put 3 stitches on cable needle, hold them in front, knit 3 from your main needle, then knit the 3 from your cable needle)"
When you do the cables, put 3 sts on a cn (slide them over with the tips facing each other). Hold those sts in front when you knit the other 3, and knit the ones on the cn. Make sure they're not twisted, lay the sts down flat so you can see them easier, then knit them off the cn. It's possible you're twisting the sts on the cn, it might help if you did this at a table or with a pillow in your lap because that first cable row is going to be very awkward. I'd even suggest you knit 3 rows first then do the cables. With a little more length to the strap it may be easier.
ETA - Also, put it down for the night. When you try to knit when you're tired it gets worse, not better. Pick it up tomorrow....