How can i return back to Mestry Island?

Hello, I was curious about this game, looking really good. So I tried to download it and launch - an error message appears saying "You are not using an authorized original version, the game has been restricted for security reasons". It gives me a choice to "exit" which does the obvious and "store" which does nothing. I did find this game on steam, downloaded on steam, so I do not understand what seems to be a problem ? :/...

What do I use to craft this?

me and my friend completed the first quest but we there is nothing else to do because there is literally nothing on the island except for the dirty skeletons

It says you need sand and water to make clay at the mortar but I am unable to even with sand and water jars. Any advice? It seems like I really need clay to progress but have no idea how to get it. Thanks!