i have a number of cordylines in my garden and generally they do re-grow as you say - however the ones that have not have gone all soft at the stem - when you pinch the stem i mean - if that has happened you could see how far down the softness goes and cut it again below that to stop the rot - they are amazing at recovering - dare i suggest patience? although if you are mid summer there i would have expected to see some shoots now as you say - sometimes the stem will die back and new shoots come up from the roots ... i do hope it recovers for you - Cate =))