It isn’t something that looks quite natural as it has to be pulled across which is probably why it doesn’t seem like it’s right.
See if this helps

First the red line.this is the left of the neck band (left as you wear it).
I’ve added a yellow arrow, bring the point of the neckband down (folded or allowed to roll over to reveal the inside) so that the corner meets the other red line where the arrow head is.
The 2 red lines join together.
At the very bottom of the V of the neckband in the photo the 2 red lines don’t need a seam as such as they are already joined right in the bottom of the V
After that left side is in place and sewn (or pinned for now) onto the right side place, then do the other side.
The green line on the neckband will seam across the other green line, however it will seam to the inside of the neckband because you will have the other side of the collar in place, revealing the inside neckedge or pickup line, imagine the green line is on the wrong side of the fabric. The purple arrow shows the point of collar and the green line which needs to fold or roll down and be pulled across to where the arrow head is pointing.
Again the other end of the green line, right in the bottom of that V opening is already joined.
Maybe pin one in place and post a photo?
What is the pattern name/number? If these 2 edges don’t want to move into place perhaps check the pattern instruction for the neckband (check maybe where to pick up and knit from and to). I am looking at a few photos of shawl collars but not seeing one with the neck knit quite like this. It might help to see a picture of the pattern photo or the neck band instruction.