White board : unable to create on it, and to save to use it later

Hello. I have a premium account and I am trying to create a whiteboard to use for an upcoming webinar. There seems to be some kind of problem with the interface, when I am trying to had a note or text or image on the board I newly created, it doesn't show. And last week, when it was still working, I closed the window after creating my design, and when I went to look at it again the next day the whiteboard was completely blanc, no design on it anymore, so a problem with the save settings I guess. I tried to go on forums, check out the settings of the whiteboard on zoom, but I can't find a solution. Does anyone has this issue? And how did you solve it? Thank you kindly for your help!