Serious question: Are you certain it's a button? (That is, can you land on it using the B browsing shortcut?)
In recent years there has been what I consider an awful trend, and that is creating links that appear visually as buttons. I'm constantly seeing things that any sane person (who can also see, literally) would presume are buttons that are not, in actuality, buttons.
If this thing is a link rather than a button you can find it with screen reader search or by bringing up the list of links and looking for a submit link.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
One does not discover new lands without consenting to lose sight of the shore for a very long time.
~ André Gide