Light fixtures

I’ve just changed 2 light fittings and seem to have a little problem! They’re both connected to the same switch. I changed the first light and everything was fine. I changed the second light and now they’re permanently on, I can only turn it off from the breaker! There are 4 cables coming out of the ceiling so I have 4 lives, earths & neutrals. 1 neutral cable has been sleeved. I’ve obviously got something in the wrong place, any idea what could be wrong?