How to use a Cats & Dogs solution
Our solver works each board from the squares shown at the start, one forced move at a time. Every step shows the board with the new squares ringed, and a short reason: two alike side by side, a gap between two alike, an = or × sign, or a row that already has its three of one animal. Nothing is guessed. Every board we publish has one answer.
Don't read the whole thing. Find the first step whose board doesn't match yours. That is the move you missed. Read it, then go back and finish the board yourself. The rules and moves are on the Cats & Dogs page.