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 ? :/...

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

What do I use to craft this?

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!