Hydro-Ban is a waterproofing material…
https://laticrete.com/en/tile-and-stone-installation/waterproofing/hydro-ban?gad=1&gclid=EAIaIQobChMI6KPWoLuu_wIV4jWtBh1IXgi4EAAYASAAEgK4rfD_BwE
Lots of potential issues here with a re-plaster, follow the NPC standards...