We had this problem for months with my son. In the end, I used bribery. I bought him a Monster High doll that he was desperate for ( don't ask ) and showed it to him, and said he could have it if he did a poo in the potty. We couldn't believe our eyes, there and then, within 30 seconds of me showing it to him, he pulled his pants down, squat on the potty and squeezed a little poo out. The family crowded round and clapped and cheered, he was so happy.
You have to find out what it is they really want and dangle it in front of them. I used this technique when my DD had urinary retention and was afraid to pass urine because her urethra burnt if she did. She had gone 24 hours without passing urine. I bribed her with a Barbie doll, and she finally did a wee in the bath. Also used it for injections and the dentist.
I've not had a problem with this but read somewhere to line the potty with a nappy when she needs poo, then after a few goes take the nappy away. Unfortunately I've not got any personal experience but it seems to be common problem so I sure someone on here should be able to help.
So resisted temptation to call this thread Sorted for Wees and Piss.
Anyway dd is 28 months. Wee pretty much sorted now - takes herself to potty or toilet unless knackered or too distracted. But will not poo other than in nappy/knickers and no amount of accidents seem enough to change this. Any ideas?