Board Game Arena

I tried to setup mermaids town on river tile, but for some reason it doesnt do anything. There is 2 blue rounded tiles where it points where I could put town, but it doesnt work. Has anyone does this before? Real life you need to put town tile on river, if its connected those 4 tiles together. One town can be done like this. Here is the game where it happened: https://boardgamearena.com/1/terramysti ... e=91631686

Forgot this. Was too fixed on those river tiles, had to choose town first.