Lines are not allowed to match. Eg line 4 and 7 are the same (which is not allowed)

There are two identical rows.

The game should show the identical rows/columns instead of just highlighting every incorrect square... it can take a while to find out what's actually wrong with a solution.

Same thing happened to me. Looks like it checks for one hard-coded answer when there could be many for a given puzzle. It should just check that your board satisfies the rules described in the tutorial instead.

Rows 4 and 7 are identical

Try flipping the horizontally adjacent blocks