My "puppy" is one year old. He still does not fully 'get it'
We have now progressed from him urinating on the sofa to him not having any accidents but needing to have someone actually stood outside with him for ten minutes while he goes, or else he will come inside without going, leave it too late and urinate along the entire length of the house while he tries a too-late-made-dash to the yard.
He also needs reminding that he probably needs the loo or he leaves it too late.
I have now realised that he only wees in the house when alone with DH. This is because his "I need a wee" signals are very, very subtle and almost identical to our other dogs "I can't find a comfy bed" signals, so instead of taking him outside DH tells him to lay down, cue weeing on the sofa.
I this far away from giving up on the pair of them.
Whippy took around four days to train, Devil Dog around a fortnight, but he was older.
They key is learning your own individual dog's cues. Sniffing the floor, pacing and circling are common "I need a wee" signs.