Has anyone tried beginning sleep training with an older baby? How old was your baby and what did you do?

We successfully sleep trained LO1 starting at 4.5 months. For various reasons we didn't really get around to starting with LO2 and he's now 14 months and refusing to lay down in his crib. When I lay him down he immediately sits up and cries. He normally co-sleeps at night with us and sleeps on a mat at daycare. His daycare teachers say he naps well.

We did extinction with LO1 and it worked well for her, but it's not working so great with LO2.

Any advice?