We tried training at 2, DD didn't get it, so we waited. Since then we have tried every few months or so but desisted once she was upset about it as I didn't see why we should keep upsetting her when the issue would sort itself eventually. But it hasn't sorted itself 
This has been our 6th attempt. DD is 4 in November. Its really the latest it can be especially as there is pressure from nursery/HV to get her sorted. She just doesn't get it, she will sit on the potty fine normally, but as soon as she actually needs a wee or a poo she gets off and just sits on the sofa or something and does it there. I just do not know what to do...surely its not normal for them to still even WANT nappies at 4 nevermind actually have to be in them? She doesn't mind when she has an accident, she doesn't tell us she is wet or anything. Also when we realize she is wet she is having huge meltdowns similar to the meltdown she has if we notice she is peeing and quickly shift her onto the potty...she doesn't seem to understand sticker charts. We even resorted tot selling her she could have a sweetie for successful poos/pees which didn't work..
I should maybe add she has a speech delay and can't really tell us what the problem is. She understands every word we say to her though.
I just need to know what to do?! HV is horrible and judgey and isn't coming out for 2 weeks anyway (to do DS 2 year check) and I will mention it to her. But I really want DD trained before she goes back to nursery next week..