Whats wrong with my vines?

Did you set up block rotation correctly?

I'm not sure if this could be the case but you should make sure it is

1. Make sure block rotation is set up to rotate around the Y axis only (North, South, East, and West) from block-face
2. IF you are using a custom model, MAKE SURE that the flat part of the model is on the southern-most side of the block

WHY Block-face rotation? Block-face rotation rotates the block based on what face of it's "parent block" you placed the block on. Similar to how logs work only it rotates a full 360 degrees around the Y axis.

WHY Does the model/texture part need to be at the southern-most end of the model? Because the part of the block that will be connected to other blocks will be the southern most end.

Other than those 2 things, you may also need an "update tick" trigger to check which direction the block is facing and to check if the block on the back side of your vines is solid as well as an "additional placement condition" procedure to check if there is a block on either x+1 or x-1 or z+1 or z-1 or if the block at y+1 is your custom vines.