Hey Eden, I hope you figured out your problem. It looks to me like the tileset is incomplete, since I don't see any tiles that would connect the two straight paths with any of the other tiles. In addition, there are no inner corners that connect to the outer corners (maybe they do connect, but in the overlay there are some markings missing that would be required for the tiles to connect as far as the Wang Brush is concerned).
Please don't hesitate to come to the Tiled Discord or the forum, where you will often find help. I'm sorry for the late reply here.