Originally posted by Leffe-(SWE):

If you had mods or haven't played for a long time the usual fix for the game not starting or behaving strange is to uninstall the game and manually remove the Valheim folder before reinstalling again.

Woah! That is a drastic solution and not likely the problem. He's a noob and it seems to me that the problem is more likely that he can't see the snap points from where he's standing. If you can't see the snap point you can't put the cursor on it. You often need need to build temporary scaffolding (stairs and floor pieces, etc) to get yourself where you need to be to see the snap point.