All my children's work is deleting

Hi there. We were really excited to use your platform this summer and my eldest has been working on the site every day. However, the site keeps deleting all of her progress. I am unable to see anything she has done and her profile doesn't show any work completed either. Is there something specific we need to do to save progress? She is getting really disheartened by this as she was working really hard on it.

Kirsty