ipad issue with white board

First let me state that I am old and not the most tech savvy. But I tutor math in zoom on my ipad and while I was using the free version things were fine. But now that I have updated to pro, to avoid the 40 min time limit, I can no longer write or even find the tools to write on the white board. Please help!! I'm so frustrated and can't a live person to talk to me.