Magic keyboard not working with Zoom screen sharing

Hi, I got a new iPad Air recently, with Pencil 2 and Magic Keyboard. One of the reasons I've been using my iPad a lot is for Zoom screen sharing markup - I'm a teacher and work with a lot of my students remotely. They screen-share their work, and then I make notes showing them how to complete their problems.

The Pencil works just fine for markup. I can draw on the student's shared screen without any issues. But the Magic Keyboard doesn't work when I try to do text markup. I know that the keyboard works in general because when I switch to another app like Safari or Google Docs, I can use it to type. But when I use the "Text" feature on Zoom markup, the keyboard doesn't respond at all. I can initiate a text box, but then the keyboard doesn't produce any input. If I bring up an on-screen keyboard, that does generate input.

Markup does work for me on Zoom in general. It's just this single function that doesn't work. I'm confused, because when I had my old iPad Pro with a Logitech keyboard, it worked just fine in this exact same environment. Is there a setting I need to adjust?