I finished a workout but my war attack is missing

The screen right after you finish shows what your phone works out on its own. Kovo's own count of that workout follows a moment later, and that is the count your war uses.

If the war screen shows nothing yet, that count has not arrived. Wait a moment, then open the war screen again.

Nothing is lost while you wait. Kovo checks again later and picks up any workout that was not counted the first time.

Learn more: How war stars work