cant get pattern to work

Hi all,I've tried so many times with the start of this pattern, however it doesnt 4 chn and join with sl st in 1st ch to form ring.Rnd 1: 3ch, 11tr in ring, sl st into 3rd ch of st-ch.Rnd 2: 3ch, 1tr in same st as sl st, *(1tr in next st, 2tr in next st) repeat from *to end of round, 1tr in las st, sl st into 3rd ch of st-ch (24 tr)Help would be most appreciated.Ta, Mia