With first needle, knit across 12 sts of heel, pick up and k 12 sts along side of heel flap, M1 between heel flap and next (instep) needle, with second needle, work 20 sts across 2 instep needles, with third needle, M1 between instep needle and heel flap, pick up 12 sts along remaining side of heel flap, work across 19 sts of heel flap – 58 sts. Place marker for beg of rnd.
Dec Rnd K 17, k2tog, k 20, k2tog, k 17.
Knit 1 rnd.
Rep last 2 rnds until 40 sts remain.
It opens for me now, they must've been busy the other day.
You can't repeat the rounds because you're decreasing.
You should K2tog one side and SSK the other side (or at least that's what I like to do so I get a mirror image).
"work across 19 sts of heel flap" is wrong. After M1, picking up 12 you should knit 6 and place the marker. That is your 19 per side.
I also find decreasing at the end of the needles give a hole (which I have on the first socks I made with this pattern).
It should be, "k to last 3 stitches, K2tog, k20, SSK, k to marker.
Rep last 2 rnds until 40 sts remain"
I think the toe is also written like that, but it starts you off right unlike the "work across 19 sts".
If you have ever made a sock these things may be second nature.
If you've never made a sock it probably won't work. I only noticed because I had made crochet socks, but I had no idea what knitted socks required.
The person who helped me on this forum said they emailed them about it and they've never changed it.