New crack in ceiling plaster

Sounds like it could be either the artex has become de-bonded from the ceiling due to either the pva mix not strong enough or was already becoming loose and the extra weight of the new plaster has made it worse or that their was crack in the ceiling that should have been screwed up and skrimmed prior to being plastered , If you get a broom and push it and it moves a tiny bit where crack if you can find where timbers are it will screw back then fill it .if its live and has become de-bonded it will need scraping back and patching or re-plastering . hope this has helped you .